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NASA 4/28/89 [OA 4423]
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Records of the White House Office of Speechwriting (George H. W. Bush Administration)
Mary Kate Grant Subject Files
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Originally Processed With FOIA(s):
FOIA Number:
S; 1999-0093-F
FOIA
MARKER
This is not a textual record. This is used as an
administrative marker by the George Bush Presidential
Library Staff.
Record Group/Collection:
George H.W. Bush Presidential Records
Collection/Office of Origin:
Speechwriting, White House Office of
Series:
Grant, Mary Kate, Files
Subseries:
Subject File, 1988-1991
OA/ID Number:
13882
Folder ID Number:
13882-007
Folder Title:
NASA, 4/28/89
Stack:
Row:
Section:
Shelf:
Position:
G
19
2
7
7
TRANSFER SHEET
BUSH PRESIDENTIAL MATERIALS PROJECT
COLLECTION
ACC.NO:
The following material was withdrawn from this segment of the
collection and trasferred to the
AUDIOVISUAL COLLECTION
BOOK COLLECTION
X
MUSEUM COLLECTION
OTHER (SPECIFY:
)
DESCRIPTION:
ONE NASA PATCH WITH THE NAMES
"CLEAVE, LEE, THAGARD, WALKER, GRABE"
ON THE OUTER EDGE.
BUSH PRES. RECORDS
OFFICE OF SPEECHWRITING - GRANT
SERIES
BOX NO.
SUBJECT FILE
FILE FOLDER TITLE:
NASA [4/28/89]
[OA- 4423]
TRANSFERRED BY:
DATE OF TRANSFER:
Robert F. Hobriss
6/12/96
RECEIVED BY:
DATE RECEIVED
Amy Day
6-17-96
NASA
National
Aeronautics and
Space
Administration
NASA Facts
National Aeronautics and
Space Administration
John F. Kennedy Space Center
Kennedy Space Center, Florida 32899
AC 407 867-2468
KSC Release No. 24-89
March 1989
STS-30
MAGELLAN
U.S. planetary exploration resumes with the
STS-30 Space Shuttle mission, which has as its pri-
mary objective the deployment of the Magellan space-
craft on its quest to map the surface of Venus.
The flight will be the fourth for the orbiter
Atlantis and the 29th Space Shuttle mission. Atlantis
will be launched from Pad 39B at Kennedy Space
Center into a 184-statute mile circular orbit inclined
28.85 degrees to the equator.
Commander of the five-member crew is David
M. Walker (Capt., USN), who piloted STS 51-A in
November 1984. Pilot Ronald J. Grabe (Col., USAF)
had the same role on STS 51-J in October 1985. The
three mission specialists are Mary L. Cleave (Ph.D.),
Norman E. Thagard, (M.D.), and Mark C. Lee (Maj.,
USAF). Cleave was a mission specialist on STS 61-B,
Thagard on STS-7 and STS 51-B; STS-30 is Lee's first
flight.
Experiment Apparatus, a joint endeavor agreement
Magellan marks the first U.S. planetary mis-
between Rockwell International and NASA, is a modu-
sion since Pioneer Venus 12 in 1978. It also kicks off a
lar zero-gravity biology, chemistry and physics labora-
core program of solar system exploration involving
tory. The Mesoscale Lightning Experiment is a NASA-
NASA and organizations from the United States and
sponsored effort involving several universities. Its ob-
jective is to study the visual characteristics of large
the international community. The 31-day launch period
scale lightning in the upper atmosphere. Atlantis will
for the mission extends from April 28 to May 28, when
act as a calibration target for a third experiment, involv-
Earth and Venus are properly aligned.
ing the Air Force Maui Optical System Facility in
The Magellan spacecraft arrived at Kennedy
Hawaii.
Space Center in October 1988 for pre-launch process-
After a four-day flight, Atlantis and her crew are
ing. In February 1989, it was mated with the Inertial
scheduled to land at Edwards Air Force Base, Calif.
Upper Stage (IUS) booster which will place it on its
Atlantis' next mission, STS-34 in October, also in-
trajectory toward Venus.
volves deployment of a planetary explorer. Galileo, a
Three middeck experiments will be conducted
spacecraft and atmospheric probe, will study Jupiter
during STS-30. All have flown before. The Fluids
and its satellites.
KSC FORM 2-203NS (REV. 6/88)
Laboratory in Pasadena, Calif., will take into account
this spacecraft motion and synthesize a much larger
antenna than the 12-foot one Magellan actually has.
Besides radar imaging, the SAR will also col-
lect radiometry data (measure of surface radiation from
which material content can be inferred) and its antenna
will serve as the telecommunications link with Earth.
Other features of the three axis-stabilized
spacecraft are a low-gain omni-antenna to receive
transmissions from Earth and a horn-shaped altimetry
antenna. Its two movable solar panels are capable of
producing up to 1,545 watts of power in Venus orbit;
two nickel cadmium batteries will supply alternative
power.
Together with its Star-48 solid rocket motor,
Magellan weighs 7,603 pounds. The Jet Propulsion
Laboratory, Pasadena, Calif., manages the Magellan
project for NASA. Prime contractor for the spacecraft
is Martin Marietta Astronautics Group, Denver, Colo.,
and for the SAR, Hughes Aircraft Co., Los Angeles,
Calif.
MAGELLAN
Deployment, Journey to Venus:
Since 1961, the United States and Soviet
Union have sent more than twenty missions to Venus,
Magellan will arrive at Venus in August 1990,
making it the most visited of Earth's fellow planets. But
after a 15-month journey through space. The trip will
include one and a half revolutions around the sun and
the Magellan Venus Radar Mapper will yield the most
detailed and comprehensive picture to date of the
two planned mid-course corrections.
The spacecraft and IUS will be deployed from
veiled planet. Magellan will map up to 90% of the
the orbiter payload bay nominally about six hours into
planetary surface with a resolution as sharp as 130
the mission. Magellan's solar panels will then be de-
yards. By contrast, the Pioneer Venus spacecraft
launched in 1978 was able to map about the same
ployed. Less than an hour later, the IUS first stage
motor will fire and then separate. Only minutes later,
amount of surface, but with a resolution of only 60
miles. The Soviets' Venera spacecraft attained better
the IUS second stage motor fires, placing Magellan on
resolution-about 1.2 miles-but mapped only about
30% of the surface near Venus' north pole.
The Magellan mission's three specific scien-
tific objectives are to improve knowledge of Venus'
NORTH
(B) TURN
SWATH
95°
structure and geologic history; its geophysics, such as
(C) PLAYBACK
OF DATA
density distribution; and its small-scale surface phys-
TO EARTH
ics, such as surface temperature and roughness.
(A) MAPPING
Spacecraft, Instrumentation:
SPACECRAFT
In keeping with the core program goal to keep
CLOSEST
TO VENUS
costs down, much of Magellan's design and flight
hardware came from earlier programs, primarily Voy-
(D) STAR
CALIBRATION
ager and Galileo. For example, its Synthetic Aperture
Radar (SAR) antenna is a flight-qualified spare from a
NOT MAPPED
Voyager spacecraft.
SOUTH
SWATH
Because Venus is obscured by a thick cloud
-95°
PLAYBACK
TURN
OF DATA
cover, radar is the mapping instrument of choice, rather
TO EARTH
than an imaging instrument which relies on optics.
Unlike conventional radar, where resolution is linked to
MISSION PHASES
antenna size, SAR uses spacecraft motion to simulate
a large antenna. Computers at the Jet Propulsion
FORWARD
(HARDWARE FROM OTHER SPACECRAFT
EQUIPMENT
INDICATED IN PARENTHESES)
STAR
MODULE
SCANNER
(GALILEO)
PROPULSION MODULE
ROCKET ENGINE
MODULE
(VOYAGER; GALILEO)
SAR & TELEMETRY
ANTENNA
THERMAL CONTROL
(VOYAGER)
LOUVERS
SOLAR PANEL DRIVE
LOW-GAIN
AND CABLE
ANTENNA
ALTIMETER
SOLAR PANEL
BUS
ANTENNA
(VOYAGER; VIKING)
MAGELLAN SPACECRAFT
its interplanetary trajectory toward Venus, and then
the same antenna will be turned toward Earth. Magel-
separates. This rapid sequential firing of the IUS mo-
lan's tape recorder will play back to Deep Space
tors means the spacecraft is not parked in an interme-
Network (DSN) ground station antennas the raw data
diate orbit, as occurs when the IUS is used to place a
it has just collected. Monitor, command and control of
spacecraft in geosynchronous Earth orbit. In the latter
the spacecraft will be from the Jet Propulsion Labora-
instance, an interval of several hours separates the first
tory, which also manages the DSN for NASA. Magel-
and second stage motor firings.
lan's Star Scanner, a navigation instrument, will be
Once Magellan arrives at Venus, the Star-48
used in conjunction with reference stars to reset the
motor will fire to place the spacecraft in its elliptical orbit
spacecraft attitude control system's pointing knowl-
around the planet. Magellan will be in a fixed polar orbit
edge during the playback phase.
and will pass nearly, but not quite, over the planet's
During the mapping phase, the SAR will image
north and south poles, coming as close as 155 miles
a swath of the Venusian surface between 10 and 17
when near the equator and moving as far away as
miles wide and 9,942 miles long, starting at or near the
4,977 miles.
north pole and continuing into the southern hemi-
After an approximately two-week checkout
sphere. Altogether, 1,852 of these immense imaging
process is completed, the spacecraft will begin its
swaths will be produced. They eventually will be com-
mapping operation. Since it takes Venus 243 Earth
pressed into mosaics which will then be made into
days to complete a single rotation, it will take the same
maps of the planet.
amount of time for nearly every point on the planet to
Magellan's altimeter will measure with up to
pass under Magellan's radar; hence, the mapping
better than 50-yard accuracy the height of surface
mission is meticulously timed to last exactly 243 days.
features. When combined with radar imaging, research-
ers will be able to catalogue the volcanic, tectonic,
Mission:
cratering and erosional processes shaping Venus.
Gravity data will be obtained through radio
Magellan's highly elliptical orbit will be divided
measurements of the minute deviations in the space-
into two phases, mapping and playback. When closer
craft's orbital path, caused by variations in the planet's
to the planet - about 35 minutes of each three and a
density.
quarter hour orbit Magellan's high gain antenna will be
Once this primary mission is completed in
pointed toward the planetary surface for radar map-
1991, and should there be adequate fuel remaining,
ping, and the data saved on an onboard tape recorder.
Magellan will map areas previously missed and per-
As the spacecraft swings away from Venus,
form gravity experiments.
ATLANTIS
The Shuttle orbiter Atlantis (OV-104) joined
NASA's fleet of reusable winged spaceships in April
1985 when it was delivered to Kennedy Space Center
for flight processing. It was ordered under a January
1979 contract with Rockwell International.
On Oct. 3, 1985, Atlantis roared off Pad 39A on
its maiden flight, STS 51-J, the second Shuttle mission
totally dedicated to the Department of Defense. On
Atlantis' second mission, STS 61-B in November 1985,
three communications satellites were deployed. The
orbiter flew its second classified Department of De-
fense mission, STS-27, in December 1988.
Like its two sister orbiters, Discovery and
Columbia, Atlantis is named for a famous sailing ship.
The Woods Hole Oceanographic Institute, a research
facility, operated a two-masted ketch named Atlantis
that traversed more than half a million miles of the
Earth's surface between 1930 and 1966.
As part of the Shuttle return-to-flight effort,
Atlantis underwent more than 200 modifications. These
included various vehicle upgrades and hardware
changes to enhance performance and provide added
safety margins. Post-STS-27 modifications included
extensive repairs to the orbiter's outer Thermal Protec-
tion System tiles.
The delta-winged spaceship looks a lot like an
airplane and is about the size of a DC-9. It is launched
into space like a conventional rocket, bolted to an
external propellant tank and two solid rocket boosters.
Kennedy Space Center engineers and techni-
cians prepare the orbiter for flight by servicing its
systems and loading cargo into its bus-sized payload
bay. They attach the orbiter to the tank and boosters on
a mobile launcher platform and the entire vehicle is
transported out to the launch pad.
After liftoff, the boosters burn for a little more
than two minutes. They are jettisoned, and parachutes
slow their descent to the Atlantic Ocean, where recov-
ery ships are waiting to retrieve the spent casings and
return them to port. The orbiter's three main engines
burn for about six more minutes following booster
separation. After the engines shut down, the external
tank is jettisoned to break up upon reentry into the
Earth's atmosphere.
The orbiter then carries out its mission in
space and returns to Earth like a glider. Planned end-
of-mission landing site is Edwards Air Force Base,
Calif. Atlantis will then be towed to NASA's Dryden
Flight Research Facility and prepared by the Kennedy
Space Center recovery team for the ferry flight back to
KSC and turnaround for its next mission.
Magellan Fact Sheet
Mission Summary
The Magellan spacecraft will be launched in April 1989 by the Shuttle and Inertial Upper Stage on an interplanetary trajectory to
Venus. The selected trajectory has a heliocentric transfer angle slightly greater than 540° and requires 15 months of flight time. Upon
arrival at Venus in August 1990, the spacecraft will use its solid rocket motor to get into an elliptical near-polar orbit around Venus.
During a mapping period of 8 months, the Synthetic Aperture Radar (SAR) will be used to obtain radar images of 70 to 90 percent
of the planet, with a resolution about ten times better than that achieved by the Soviets' Venera 15 and 16 missions. Precise radio
tracking of the spacecraft will provide gravity information. The resulting geological maps will permit the first global geological
analysis of the planet comparable to those that have been done for the other planetary bodies of the inner solar system.
Venus
Venus at
Arrival
Radius: 6051 km
(8/10/90)
Rotational Period: 243 Earth days
Earth
Orbit Period: 225 Earth days
Venus at
Orbit
Distance from Sun: 1.1 X 10⁸ km
Launch
Average Density: 5.2 g/cm³
Surface Gravity: .907 times that of Earth's gravity
Venus
Orbit
Atmospheric Pressure at Surface: 90 times that of
Vernal
Earth's surface
Equinox
Temperature at Surface: 850°F (730°K)
SUN
Atmospheric Composition: Carbon dioxide (96%); nitrogen
(3+%); trace amounts of sulfur dioxide, water vapor,
Earth at
carbon monoxide, argon, helium, neon, hydrogen chloride,
Launch
Earth at
hydrogen fluoride
4/28/89
Arrival
Major Mission Characteristics
Launch Date: April 28 - May 27, 1989
Launch Vehicle: Shuttle/IUS (2 stage)
Interplanetary Cruise: 442 - 468 days
Venus Arrival: August 10, 1990
Mapping Orbit Period: 3.15 hours
Radar Mapping: 37 minutes/orbit
Mapping Orbit Inclination: 86°
Superior Conjunction (SC): October 26 - November 9, 1990
End of Nominal Mission: April 28, 1991
Data Gap Recoverable: June 27 - July 10, 1991
<
The Magellan spacecraft employing
SAR to pierce Venus' cloud
cover and map its surface
Mission Objectives
To obtain near global (>70% coverage) radar images of the planet's surface, with resolution equivalent to optical imaging of
1 km per line pair
To obtain a near global topographic map with 50km spatial and 100m vertical resolution
To obtain near global (>76%) gravity field data with 700km or better resolution and 2-3 milligals accuracy
To develop an understanding of the geological evolution of the planet, principally its density distribution and dynamics
Mission Timeline
Magellan Team
Launch Period (4/28/89-5/27/89)
Solar System Exploration Division
- Gravity: William Sjogren (JPL)
Interplanetary Cruise (442-468 days)
Venus Orbit Insertion (8/10/90)
- William L. Piotrowaki, Program
- Gravity: Michel LeFebvre (CNES)
Test and Calibration (17 days)
Manager
Radar Mapping (243 days)
Joseph M. Boyce, Program Scientist
System Contractors
Superior Conjunction Gop (11/2/90)
Gap Recovery
JPL
- Spacecraft: Martin
End of Nominal Mission (4/28/91)
End of Project (9/30/91)
- John H. Gerpheide, Project Manager
Marietta/Denver,
Potential Extended Mission (4/29/91 to...)
- Anthony J. Spear, Deputy Project
Charles D. Brown, Manager
Manager
Radar Sensor: Hughes Aircraft,
- R. Stephen Saunders, Project
Robert R. Mullen, Manager
Jan
Jul
Jan
Jul
Jan
Jul
Jan
Scientist
1989
1990
1991
1992
Principal Investigators
Review Board
- SAR & Altimeter. G. Pettengil (MIT)
Kane Casani, Chairman (JPL)
+Zₛ
Key Spacecraft Characteristics
HGA (3.7m diameter) used both as radar antenna and as
High Gain Antenna
telecommunications antenna
(Voyager)
ALTA
Spare GLL CDS reconfigured to MGN specifications
Single science instrument operates in SAR, altimeter,
and radiometer modes
Forward Equipment Module
Propellant Tank
(Shuttle APU)
Radio subsystem used for gravity data acquisition
+
Equipment Bus
Powered by solar panels with rechargeable batteries
Solar Array
(Voyager)
(2 each)
Star-48B solid rocket motor for Venus Orbit Insertion
Monopropellant thruster system (0.9 to 445N) with
STAR-48 SRM
(PAM-D)
133kg Hydrazine
Spacecraft injected mass of 3475 kg
Spacecraft on-orbit dry mass of 1046 kg
Spacecraft - Cruise Configuration
Orthogonal reaction wheels (3) used for spacecraft
control
Key Radar Sensor Characteristics
X-band downlink 268.8 kbps
Entry
Synthetic Aperture Radar (SAR)
Begin Mapping
- Frequency
2.385 GHz
- Operating Altitude
250 2100 km
- Look Angle
14° - 44° (from nadir)
- Swath Width
25 km (variable)
- Pulse Length
26.5 msec
Data Transmission
Periapsis
- PRF
4400-5800 Hz
to DSN
- Peak Power
325 W
- Quantization
2 bits
- Data Acquisition Rate
806 kbps
Operates in SAR, altimeter, and radiometer modes
- SAR Resolution
300m range/
Exit
150m azimuth
End Mapping
- Altimeter Resolution
30m
- Radiometer Accuracy
2°C
Operating parameters controlled via ground command
Magellan Mapping/Telecommunications Attitude
80°
Orbital Mapping Characteristics
95°
Turn
Retrace
Playback
56.6 min
DSN Lockup
6.0
North
4.7
1 min
min
Swath
Mapping Frequency
1 swath/orbit
268.8 kbps
min
Record Rate
806.4 kbps
Record Duration
37.2 min (maximum)
Periapsis
Playback Duration
114 min
North Swath
250 km
Tape Recorder Capacity
1.8 X 10° bits
Orbit
Period = 3.15 hr
South Swath
Data Accumulation Rate
Orbit
1.37 X 10¹⁰ bits/day
STARCAL
STAR A
Command Upload Frequency
3/week
(14.0 min)
B
STAR B
Mapping True Anomaly Range
-80 to +80 deg
A
Mapping Record
Mapping Altitude Range
250 to 2100 km
Apoapsis
37.2 min
DSN Lockup
Swath Width
806.4 kbps
25 km (variable)
Momentum
1 Min
4.7
Desaturation
min
-66°
Daily Planet Coverage Increase
0.4 percent
Not
Mapped
Idle
Duration of Mapping Mission
243 days
South
-80° Swath
Nominal Latitude Range of
Turn
Planet Mapped
+90 to -67.2 deg
Playback
Margin
6.0 min
57.1 min
5.4 min
Periapsis
250 km
268.8 kbps
Apoapsis
8029 km
WLP 9/88
STAR
VENUS AT ARRIVAL
NASA
FORWARD
SCANNER PROPULSION MODULE
8/10/90
EQUIPMENT MODULE
VENUS AT
LAUNCH
4/28/89
ROCKET
National Aeronautics and
ENGINE
MODULE
EARTH
Space Administration
HIGH-GAIN
ORBIT
ANTENNA
THERMAL
MAGELLAN
CONTROL
ORBIT
VERNAL
LOUVERS
SOLAR PANEL
VENUS
EQUINOX
Jet Propulsion Laboratory
LOW-GAIN
DRIVE AND
ORBIT
California Institute of Technology
ANTENNA
CABLE WRAP
EARTH AT
0
EARTH AT
Magellan
BUS
LAUNCH
ARRIVAL (VOI)
Pasadena, California
4/28/89
8/10/90
P-31315
ALTIMETER
ANTENNA
SOLAR PANEL
This artist's rendering shows the Magellan spacecraft in an elliptical orbit around Venus and illustrates the mapping and data-transmission phases
of the mission. During the mapping phase, the spacecraft will turn its large antenna toward Venus. For 37 minutes, the Synthetic Aperture Radar
(SAR) will map a 15-mile-wide swath from the north pole to 66 degrees south latitude, acquiring imaging, altimetry and radiometry data. As the
spacecraft reaches the high point of its orbit, the antenna will be turned toward Earth and, for 115 minutes, the data will be transmitted to Earth
receiving stations.
Magellan Mission
Scheduled for launch in 1989, the Magellan spacecraft will conduct the most comprehensive observation of the surface and gravitational
features of Venus ever undertaken. During its 243-day (one Venus rotation) primary mission, the spacecraft will map up to 90 percent of the
planet with high-resolution imaging radar and will return more digital imaging data than all previous U.S. planetary missions combined. Lifted
into Earth orbit by a shuttle, Magellan will be sent on its 15-month journey to Venus by an Inertial Upper Stage (IUS) booster rocket. On
arrival at Venus in 1990, a solid rocket motor will insert the spacecraft into an elliptical orbit and then will be jettisoned. For 37 minutes of
each orbit, the imaging radar, called Synthetic Aperture Radar or SAR, will image a 15-mile-wide swath of Venus' surface while also acquiring
altimetry and radiometry data to determine the altitudes and temperatures of surface features. Then, as the spacecraft moves toward the high
point of its orbit, Magellan will turn its large antenna toward Earth and, for 115 minutes, will transmit the radar data at 268 kilobits (1 kilobit
equals 1,000 bits of data) per second to Earth receiving stations. Also during this period, gravity data will be acquired as small accelerations
of the spacecraft are measured from Earth.
JPL 400-344D 9/88
STAR
VENUS AT ARRIVAL
NASA
FORWARD
SCANNER PROPULSION MODULE
8/10/90
EQUIPMENT MODULE
VENUS AT
LAUNCH
4/28/89
ROCKET
ENGINE
National Aeronautics and
MODULE
EARTH
HIGH-GAIN
ORBIT
Space Administration
ANTENNA
THERMAL
MAGELLAN
-
CONTROL
ORBIT
VERNAL
LOUVERS
VENUS
EQUINOX
SOLAR PANEL
LOW-GAIN
DRIVE AND
ORBIT
Jet Propulsion Laboratory
ANTENNA
CABLE WRAP
EARTH AT
EARTH AT
LAUNCH
California Institute of Technology
BUS
ARRIVAL (VOI)
4/28/89
8/10/90
Magellan
ALTIMETER
Pasadena, California
ANTENNA
SOLAR PANEL
P-25316ac
Venus, our nearest planetary neighbor and one of the brightest objects in the night sky, is perpetually
hidden by thick clouds of carbon dioxide and sulfuric acid. Since the 1960s, scientists have used
ground-based radio telescopes to bounce radar waves off the surface and, with the aid of computer
processing, have produced images of the planet beneath the clouds. During the past two decades,
Venus has become the most visited world in the solar system. Five American and 15 Soviet spacecraft
have probed its clouds, measured its atmosphere and, with automated landers, photographed small
portions of its surface. Venus is very similar to Earth in size and volume, but its surface is a scorching
900 degrees Fahrenheit and its atmospheric pressure is 90 times that of Earth. Venus has no water, and
no magnetic field has been detected. Unlike most other planets, Venus rotates very slowly in a retrograde
direction (clockwise as viewed from the north pole). One Venus day is equal to 243 Earth days. This image
was obtained by the Pioneer Venus Orbiter in 1979.
Magellan Mission
Scheduled for launch in 1989, the Magellan spacecraft will conduct the most comprehensive observation
of the surface and gravitational features of Venus ever undertaken. During its 243-day (one Venus rota-
tion) primary mission, the spacecraft will map up to 90 percent of the planet with high-resolution imaging
radar and will return more digital imaging data than all previous U.S. planetary missions combined. Lifted
into Earth orbit by a shuttle, Magellan will be sent on its 15-month journey to Venus by an Inertial Upper
Stage (IUS) booster rocket. On arrival at Venus in 1990, a solid rocket motor will insert the spacecraft
into an elliptical orbit and then will be jettisoned. For 37 minutes of each orbit, the imaging radar, called
Synthetic Aperture Radar or SAR, will image a 15-mile-wide swath of Venus' surface while also acquiring
altimetry and radiometry data to determine the altitudes and temperatures of surface features. Then, as
the spacecraft moves toward the high point of its orbit, Magellan will turn its large antenna toward Earth
and, for 115 minutes, will transmit the radar data at 268 kilobits (1 kilobit equals 1,000 bits of data) per
second to Earth receiving stations. Also during this period, gravity data will be acquired as small accelera-
tions of the spacecraft are measured from Earth.
JPL 400-344C 9/88
STAR
VENUS AT ARRIVAL
NASA
FORWARD
SCANNER PROPULSION MODULE
8/10/90,
EQUIPMENT MODULE
VENUS AT
LAUNCH
4/28/89
ROCKET
ENGINE
National Aeronautics and
MODULE
EARTH
HIGH-GAIN
ORBIT
Space Administration
ANTENNA
THERMAL
MAGELLAN
-
CONTROL
ORBIT
VERNAL
LOUVERS
VENUS
EQUINOX
SOLAR PANEL
LOW-GAIN
DRIVE AND
ORBIT
Jet Propulsion Laboratory
ANTENNA
CABLE WRAP
EARTH AT
EARTH AT
BUS
LAUNCH
ARRIVAL (VOI)
California Institute of Technology
4/28/89
8/10/90
Magellan
ALTIMETER
Pasadena, California
ANTENNA
SOLAR PANEL
P-33264bc
The Magellan spacecraft, attached to an Inertial Upper Stage (IUS) rocket, will be carried into low Earth-
orbit by the space shuttle in 1989. After six orbits of Earth, the spacecraft will be deployed from the
shuttle's cargo bay. When the shuttle is safely 25 miles away from Magellan, the IUS will ignite and the
spacecraft will begin its journey to Venus, traveling one and one-half times around the Sun and departing
slightly from the Earth's orbital plane to intercept Venus 15 months later. JPL's Photography Group used
models of the space shuttle, the Magellan spacecraft and the IUS to create this photograph.
Magellan Mission
Scheduled for launch in 1989, the Magellan spacecraft will conduct the most comprehensive observation
of the surface and gravitational features of Venus ever undertaken. During its 243-day (one Venus rota-
tion) primary mission, the spacecraft will map up to 90 percent of the planet with high-resolution imaging
radar and will return more digital imaging data than all previous U.S. planetary missions combined. Lifted
into Earth orbit by a shuttle, Magellan will be sent on its 15-month journey to Venus by an Inertial Upper
Stage (IUS) booster rocket. On arrival at Venus in 1990, a solid rocket motor will insert the spacecraft
into an elliptical orbit and then will be jettisoned. For 37 minutes of each orbit, the imaging radar, called
Synthetic Aperture Radar or SAR, will image a 15-mile-wide swath of Venus' surface while also acquiring
altimetry and radiometry data to determine the altitudes and temperatures of surface features. Then, as
the spacecraft moves toward the high point of its orbit, Magellan will turn its large antenna toward Earth
and, for 115 minutes, will transmit the radar data at 268 kilobits (1 kilobit equals 1,000 bits of data) per
second to Earth receiving stations. Also during this period, gravity data will be acquired as small accelera-
tions of the spacecraft are measured from Earth.
JPL 400-344B 9/88
USA
STAR
VENUS AT ARRIVAL
NASA
FORWARD
SCANNER PROPULSION MODULE
8/10/90
EQUIPMENT MODULE
VENUS AT
LAUNCH
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ROCKET
ENGINE
National Aeronautics and
MODULE
EARTH
HIGH-GAIN
ORBIT
Space Administration
ANTENNA
THERMAL
MAGELLAN
-
CONTROL
ORBIT
VERNAL
LOUVERS
VENUS
EQUINOX
SOLAR PANEL
LOW-GAIN
DRIVE AND
ORBIT
Jet Propulsion Laboratory
ANTENNA
CABLE WRAP
EARTH AT
EARTH AT
California Institute of Technology
BUS
LAUNCH
ARRIVAL (VOI)
4/28/89
8/10/90
Magellan
ALTIMETER
Pasadena, California
ANTENNA
SOLAR PANEL
P-32876
The Magellan spacecraft is being prepared for testing in Denver, Colorado, at Martin Marietta Astronautics,
prime contractor for the spacecraft. To save costs, several major pieces of Magellan's hardware are spares
from the Voyager, Galileo, Viking and Ulysses projects. The spacecraft is topped by a 12-foot-diameter
dish antenna (from the Voyager Project), which will acquire imaging and radiometry data and will com-
municate with Earth stations. Attached to the dish is a horn-shaped antenna that will be used to measure
the height of surface features. Two solar panels with a total collecting surface of about 15 square yards
will provide nearly 1,200 watts of electrical power. Most of the major parts of the spacecraft are wrapped
in reflective white thermal blankets to maintain temperature control.
Magellan Mission
Scheduled for launch in 1989, the Magellan spacecraft will conduct the most comprehensive observation
of the surface and gravitational features of Venus ever undertaken. During its 243-day (one Venus rota-
tion) primary mission, the spacecraft will map up to 90 percent of the planet with high-resolution imaging
radar and will return more digital imaging data than all previous U.S. planetary missions combined. Lifted
into Earth orbit by a shuttle, Magellan will be sent on its 15-month journey to Venus by an Inertial Upper
Stage (IUS) booster rocket. On arrival at Venus in 1990, a solid rocket motor will insert the spacecraft
into an elliptical orbit and then will be jettisoned. For 37 minutes of each orbit, the imaging radar, called
Synthetic Aperture Radar or SAR, will image a 15-mile-wide swath of Venus' surface while also acquiring
altimetry and radiometry data to determine the altitudes and temperatures of surface features. Then, as
the spacecraft moves toward the high point of its orbit, Magellan will turn its large antenna toward Earth
and, for 115 minutes, will transmit the radar data at 268 kilobits (1 kilobit equals 1,000 bits of data) per
second to Earth receiving stations. Also during this period, gravity data will be acquired as small accelera-
tions of the spacecraft are measured from Earth.
JPL 400-344A 9/88
FORK LIFT POINT
t
FORK LIFT POINT
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DD NOT LIFT WITH FLIGHT
HARDWARE ATTACHED
NASA
Shuttle Mission STS-30
Prelaunch Profile
Orbiter: (OV 104) Atlantis
Alternate deployment opportunities
Altitude: 160 nautical miles
are available on orbits 6 and 7, with
Inclination: 28.85 degrees
additional back-up deployment
Mission Duration: 4 days
opportunities available throughout
flight day 2.
Crew
David M. Walker, Commander
Magellan will be carried into low Earth
Ronald J. Grabe, Pilot
orbit by the Atlantis, then deployed
Norman E. Thagard, Mission
from the cargo bay into its own orbit
with the IUS rocket motor attached to
Specialist
its base. After several revolutions
Mary L. Cleave, Mission Specialist
Mark C. Lee, Mission Specialist
around the Earth, and spacecraft
check-out, the IUS will fire to boost
Magellan toward the planet Venus.
Payloads
Magellan Spacecraft
Magellan is scheduled to arrive at
Venus on August 10, 1990. The first
Middeck Payloads
30 days in orbit around Venus will be
Fluids Experiment Apparatus (FEA)
devoted to orbit adjustment and
Mesoscale Lightning Experiment
instrument check out. Magellan's
(MLE)
primary mission through April 1991 is
to map 70 to 90 percent of the
Highlights
planet's surface for the first time,
using a synthetic-aperture radar (SAR)
The Magellan mission marks a return
instrument.
of the United States to planetary
exploration - - the first planetary
As Magellan passes over the surface
spacecraft to be launched in nearly
of Venus, its dish antenna will look
12 years. It also holds the distinction
downward and to the side of the
of being the first planetary probe to
spacecraft's orbital path. The SAR
be launched aboard the Space
antenna will illuminate an area 15
Shuttle. And, it will be the first to use
miles wide with rapid radar pulses,
a complex, suncircling "type 4"
then record the returning signals.
trajectory to reach a planet.
Each point on the planet's surface
can be located. A measurement of the
The primary objective of this flight is
time it takes for the radar signal to
to successfully deploy the Magellan
return to Magellan will give the
spacecraft. Deployment of Magellan
spacecraft's distance to that point.
is scheduled for revolution 5 of the
mission. The first stage burn of the
Magellan will pass closest to the
Inertial Upper Stage (IUS) will begin
surface just north of the equator at 10
at deployment plus one hour and last
degrees Venus latitude, then will move
for two minutes and 30 seconds. The
up over the north pole and around the
second stage burn follows and lasts
planet in a wide loop. As a result of
for one minute and 42 seconds.
this elliptical orbit, Magellan will only
be close enough to the surface to
growth biological materials, and living
conduct mapping operations for about
organisms. FEA has the functional
35 minutes out of each three-hour
capability to heat, cool, expose to
orbital period. The rest of the time
vacuum, and manipulate experimental
will be spent transmitting the raw data
samples that can be gaseous, liquid,
from the just-completed mapping pass
or solid. Samples can be mixed and
and receiving telemetry instructions
stirred in containers or processed in a
from the Earth, or calibrating the
semi-containerless float-zone mode.
spacecraft's navigation and guidance
system. Transmissions will be received
by the large antennas of the Deep
Mesoscale Lightning Experiment
Space Network, then relayed to the
(MLE)
Jet Propulsion Laboratory in
Pasadena, California, where images
The Mesoscale Lightning Experiment
of the Venusian surface will be
is designed to obtain nighttime images
constructed by computers.
of lightning in an attempt to better
understand the effects of lightning
Since it will take 243 days for every
discharges on each other, on nearby
point on the surface to pass once
storm systems and on storm
under Magellan's gaze, the mapping
microbursts and wind patterns and to
operations are planned to take exactly
determine interrelationships over an
243 days. After completion of the
extremely large geographical area.
primary mission, an extended mission
may be undertaken, during which
The experiment will use Shuttle
areas that were missed would
payload cameras to observe lightning
be mapped, and additional data of
discharges at night from active
particularly interesting areas could
storms. Using color video cameras
be taken.
and a 35mm hand-held camera, the
experiment will provide synoptic
More than any other single mission,
coverage of an area roughly 200 by
Magellan is expected to unveil the
150 miles directly below the Shuttle.
secrets of the Venusian past, just as
Mariner 9 revealed the unsuspected
Three co-investigators will analyze the
richness of Martian geology in 1972.
lightning data taken from the Shuttle
as well as corroborate information
received from the ground-based
Middeck Payloads
lightning monitoring network. They are
Dr. Bernard Vonnegut, State
Fluids Experiment Apparatus (FEA)
University of New York, Albany;
The Fluids Experiment Apparatus is a
Dr. Max Brook, New Mexico Institute
modular, zero-gravity biology,
of Mining and Technology, Socorro;
chemistry, and physics laboratory. It
and Otha H. Vaughn Jr., NASA
supports space processing research
Marshall Space Flight Center, (MSFC),
in general liquid chemistry, fluid
Huntsville, Alabama. Richard E.
physics, thermodynamics, crystal
Valentine, MSFC, is the mission
manager.
STS-30 Distinguished Guests Schedule
Friday, April 28, 1989
Friday, April 28
10:00 a.m. Depart Andrews Air Force Base for Cape Canaveral Air
Force Station. (Brunch served enroute.)
12 Noon
Arrive Cape Canaveral Air Force Station.
Board buses for Spaceport USA.
12:30 p.m. Briefing in the Galaxy Theater Spaceport USA
Welcome: Forrest McCartney, Director of KSC (5 min)
Remarks: Dale D. Myers, NASA Acting Administrator
(5 min.)
Remarks: Richard H. Truly, NASA Administrator-
Designate (5 min.)
Remarks: Dr. Lennard Fisk, Associate Administrator,
Space Science and Applications (20 min)
Presentation: Astronaut Charles Bolden. Discusses
deployment of Magellan spacecraft (10 min)
Introduction and viewing of 15 minute film about
Magellan and its mission.
1:30 p.m. Depart Galaxy Theater for Guest Viewing Site at
Banana Creek.
1:45 p.m.
Arrive Banana Creek.
2:24 p.m. Launch of Magellan (23 minute window).
2:45 p.m. Depart Viewing Site for tour of Vehicle
Assembly Building (VAB).
3:00 p.m. Tour VAB.
3:45 p.m. Depart VAB for Shuttle Landing Facility. (SLF)
4:00 p.m. Depart SLF for Washington. (Light dinner
served enroute.)
6:00 p.m. Arrive Andrews Air Force Base.
Magenan
The Unveiling of Venus
O
f all the planets in the solar
system, Venus is the most
like our own Earth in size, mass, and
distance from the Sun. The motions
of our planetary "twin" were known
to the ancients, and its apparent
changes in shape, similar to the
phases of the Moon, were first
studied by Galileo more than four
but it also is limited-Venus always
centuries ago. In the modern era,
shows the same hemisphere to us
Venus has been one of the most
when it is near enough in its orbit for
visited planets in the solar system-
high-resolution study, so only a
20 spacecraft from the Soviet Union
fraction of the planet can be explored
and the United States have been sent
from Earth.
there since the early 1960s. Venus'
sulfur-yellow clouds have been
Therefore, in the late 1970s and early
probed, its atmospheric structure and
1980s, the United States and the
composition have been measured,
Soviet Union sent the Pioneer Venus
and automatic landers have
and Venera spacecraft, respectively,
photographed portions of its
to study Venus more closely and to
landscape and chemically analyzed
image its surface with radar. These
its rocks.
missions have answered many of our
questions about Venus' atmosphere
Yet, for all our fascination with
and large-scale surface features.
Venus, we have only a sketchy,
However, many more questions
general knowledge of the planet's
remain unanswered about the extent
surface. While the faces of the other
to which Venus' surface has been
"terrestrial" planets-Earth, Mars,
shaped by volcanoes, plate tectonics,
and the lighted sides of Mercury and
impact craters, and water and wind
the Moon-have long since been
erosion.
mapped, details of Venus' face are
still largely unknown, due to the
To help answer these remaining
planet's dense, constant cloud cover.
questions, NASA plans to launch a
The clouds prevent us from
new radar imaging spacecraft,
photographing the solid surface from
Magellan (named for the 16th century
space with conventional cameras.
explorer Ferdinand Magellan), from
the space shuttle Atlantis in April
Since the early 1960s, scientists have
1989. Arriving at Venus in August
used radar to counter this problem.
1990, Magellan will spend eight
Unlike visible light, radar waves
months mapping most of the planet
penetrate the Venusian clouds and
at a resolution (a measure of the
reflect off the solid planet back to
smallest objects that can be seen in
Earth. With the help of computer
its map) nearly ten times better than
processing, these radar reflections
that of any previous spacecraft views
can be turned into pictures of the
of the surface. More than any other
Venusian surface. Earth-based radar
single mission, Magellan is expected
imaging is thus extremely valuable,
to unveil the secrets of the Venusian
past, just as Mariner 9 revealed the
unsuspected richness of Martian
geology in 1972. In 1990, for the
first time, we will really come to know
the face of our planetary "twin."
THE PREVIOUS RADAR MISSIONS
In 1978, NASA launched the Pioneer Venus Probe and Orbiter mission to conduct the most comprehensive investigation
of Venus undertaken to date. Most of the experiments concerned the planet's atmosphere, but the orbiting spacecraft also
carried a radar system that mapped 92 percent of the surface with a resolution of about 50 to 140 kilometers (30 to 84
miles). For the first time, planetary scientists had a global map of Venus. This map showed the existence of continent-
like highlands (Aphrodite and Ishtar), hilly plains, large volcano-like mountains, and flat lowlands. However, as important
as this radar map is, it shows only large-scale features. The hills and valleys, craters and lava flows-the telling details
of Venusian geology-are as yet uncharted.
Five years after the Pioneer mission, in 1983, the Soviet Union sent
two Venera spacecraft to map Venus at a resolution of approximately 2 to 4 kilometers (1.2 to 2.4 miles). Because of
the nature of their orbits around the planet, the spacecraft were able to map only about 25 percent of the surface, near
the north pole. In comparison, Magellan will map 70 to 90 percent of the planet at a resolution varying from 250 to 750
meters (820 to 2,461 feet).
THE MAGELLAN SPACECRAFT
A key feature of the Magellan spacecraft is the economy and relative simplicity of its design. To save costs, spare
hardware has been used from other planetary projects, notably Voyager and Galileo. The 3,449-kilogram (7,604-pound)
spacecraft has only one science instrument: a radar sensor. This one instrument, however, will perform three important
functions: collecting imaging data of the surface of Venus, acquiring altimetric data of the planet's topography, and
measuring the natural thermal emissions from the Venusian surface. Magellan's only visible moving parts are a pair
of 3.5 by 3.5 meter (11 by 11 foot) square panels that collect solar energy for charging the spacecraft's nickel-cadmium
2
T W 0
-
MM
LIFT POINT
FORK LIFT POINT
The Magellan spacecraft is prepared for
testing in Denver, Colorado, at the Martin
Marietta Astronautics Group, prime contractor
for the spacecraft. Most of Magellan's major
parts are wrapped in reflective white thermal
blankets to maintain temperature control.
The spacecraft's radar sensor was built by the
Hughes Aircraft Company of El Segundo, California.
batteries.
Magellan's 3.7-meter-diameter (12-foot-diameter) high-gain antenna dish (used both for radar imaging
and for communicating with Earth) and the ten-sided "bus," which contains some of the electronics subsystems, were both
spares from the Voyager Project.
THE RADAR
With conventional radar, the resolution of an image depends on antenna size: the bigger the antenna, the better the
resolution. A large. antenna on a spacecraft, however, would be expensive and difficult to manipulate. To solve this
problem, the signals from Magellan's synthetic aperture radar (SAR) will be computer-processed on Earth SO that they
will imitate, or synthesize, the behavior of a large antenna on the spacecraft. Through this synthesis, the onboard radar
sensor will operate as if it has a huge antenna and will produce high-resolution images, even though the antenna is only
3.7 meters (12 feet) in diameter. This computerized process of "aperture synthesis" is what gives SAR its resolving power
as well as its name.
As Magellan passes over the Venusian surface, its dish antenna will look downward and to
the left side of the spacecraft's orbital path. For 37.2 minutes, the SAR antenna will emit several thousand radar pulses
each second. Traveling at the speed of light, the pulses will strike and illuminate a 25-kilometer-wide (16-mile-wide)
swath of the planet's surface, and then will immediately bounce back and be received at the instrument.
By
recording the returned pulses, we can use two measurements on each pulse to locate each point on the planet's surface.
The first measures the time it takes for the radar signal to return to Magellan; this will give the spacecraft's distance (or
range) to that point. The second carefully measures the returned signals for their Doppler effect, a shift in frequency
caused by the spacecraft's motion over the surface. This second measurement will give the location of the point with
reference to the spacecraft's line of flight, since Magellan will be either approaching or receding from the point at any
4
FOUR
ORBITAL PATH
X
synthetic ance sing be works: map time to two to image the it Any aperture takes point point can for (determined be radar in located the
A
the
return
used the signal amount by (a of of Doppler to Magelladar
ILLUMINATED
LINES
LINES
DOPPLER SHIPLER SHIP
idely same and its separated wever, B shown points s shift. motion two the as
ground one (A as of a to track the left ofthe will only be
- Iberefore radar show map will The
radar Venera miss / from left shown of only be Venusian the is a Soviet
given time.
Since each point in the radar image will have a unique range and Doppler shift, these two coordinates,
together with knowledge of the angle of the antenna's line of sight with respect to the surface, are all that is needed to
determine the location of any returned signal. The brightness of the image at that point then becomes an element of the
map image.
Through this technique, data will be collected by the radar instrument and radioed back to Earth,
where images of the Venusian surface will be constructed by computers at the Jet Propulsion Laboratory. In these images,
it will be possible to distinguish features as small as 250 meters (820 feet) for the equatorial regions of the planet (where
Magellan will pass closest to the surface) and about 750 meters (2,461 feet) near the poles. By comparison, the best
existing ground-based and spacecraft maps of Venus show no features smaller than 2,000 meters (6,562 feet).
APRIL 1989 TO AUGUST 1990: FROM EARTH TO VENUS
In late April 1989, Magellan will be carried into low Earth orbit by the space shuttle Atlantis. After several revolutions
around Earth, the spacecraft, with an Inertial Upper Stage (IUS) booster attached to its base, will be deployed from Atlantis'
cargo bay into its own orbit. After two-thirds of another revolution around Earth, the IUS will fire and propel the Magellan
spacecraft toward Venus. The IUS will then be jettisoned.
The launch period will begin on April 28 and will last
for 30 days. During this launch period, Venus will be approximately 255 million kilometers (158 million miles) from Earth.
After launch, it will take just under 15 months for Magellan to reach its destination. Three adjustment maneuvers along
the way will keep the spacecraft on time and on target for its rendezvous with Venus.
When Magellan arrives at
Venus in early August 1990, a solid rocket motor attached to the spacecraft will fire to place Magellan in orbit around the
planet. After a few adjustment maneuvers, the spacecraft will be in an elliptical orbit, with its lowest point at an altitude
of 250 kilometers (155 miles) above the planet's surface and its highest point at 8,029 kilometers (4,989 miles). The time
6
SIX
VENUS AT
ARRIVAL
VENUS AT
LAUNCH
MERCURY
ORBIT
EARTH
ORBIT
SUN
MARS
ORBIT
VERNAL
EQUINOX
VENUS
ORBIT
EARTH AT
ARRIVAL
8/10/90
EARTH AT
LAUNCH
4/28/89
This depiction of
Magellan's interplanetary
trajectory shows the orbits
of the four inner planets, as well as
the positions of Earth and Venus at the
times of the spacecraft's launch and of
its arrival at Venus. Magellan will
travel an elliptical flight path one and
one-half times around the Sun before
intercepting Venus. A traditional
trajectory to Venus would use
approximately one-half of a revolution
around the Sun; however, shuttle launch
scheduling has dictated the longer
trajectory for Magellan.
required for Magellan to make one complete orbit around Venus-the orbit period-will be three hours and nine minutes.
Since the orbit will be tilted four degrees to the axis of Venus, the spacecraft will pass nearly, but not quite, over both
the north and south poles.
AUGUST 1990 TO APRIL 1991: MAPPING THE VEILED PLANET
Although Venus is very much like Earth in size and mass, the veiled planet's rotation on its axis has several peculiar and
unexplained differences. One is that Venus turns in the opposite direction from the way Earth does, spinning on its axis
from east to west, SO that the Sun rises in the west and sets in the east. Another is that the Venusian "day" is very long-
it takes 243 of our Earth days for the planet to turn once on its axis. Since Magellan will be in a fixed, nearly polar orbit
around a very slowly turning planet, it will take 243 days for most of the surface to pass under the spacecraft's gaze once.
Thus the mapping will take 243 days.
The arrival date at Venus, August 10, 1990, will place Magellan in Venus
orbit approximately three months before superior conjunction (the passage of the planet behind the Sun as seen from
Earth). During superior conjunction, radio interference from the Sun's atmosphere will make it impossible to communicate
with the spacecraft and to conduct the radar mapping. The resultant gap in mapping coverage can be filled in during
subsequent 243-day mapping cycles.
Circling the planet every three hours and nine minutes, Magellan will pass
closest to the surface just north of the equator, at 10 degrees Venus latitude, and will then move down around the south
pole and around the planet in a wide loop. Because of this elliptical orbit, Magellan will be close enough to the surface
to conduct mapping operations for only about 37 minutes out of each three-hour orbital period. The rest of the time will
be spent transmitting the recorded raw data from the just-completed mapping pass, receiving telemetry instructions from
Earth, and calibrating the spacecraft's attitude control system with reference stars.
During mapping operations,
8
EIGHT
The 3.15-hour elliptical orbit of Magellan
will be divided into distinct phases. When
the spacecraft is closest to Venus, the antenna
will point at the planet and the radar will map
the surface (A), alternating between north and
south swaths on successive passes. After radar
operations are completed, the spacecraft will turn
to point its antenna toward Earth (B) so that data
can be transmitted (C). After calibration of the
spacecraft's attitude control subsystem (D) and
another data playback, Magellan will turn its
attention once again to the surface.
TURN
90° N
NORTH
PLAYBACK
SWATH
OF DATA
TO EARTH
(A) MAPPING
SPACECRAFT
CLOSEST
TO VENUS
(10° N)
(D) ATTITUDE
CONTROL
CALIBRATION
NOT
56° S
MAPPED
(C) PLAYBACK
70° S
OF DATA
TO EARTH
(B) TURN
SOUTH
SWATH
the high-gain antenna dish will point toward the surface of Venus. In addition to acquiring radar imaging data, the radar
sensor will use a separate fan-beam horn antenna aimed at the surface directly beneath the spacecraft to conduct
Magellan's altimetry experiment. Radar pulses from this antenna will bounce off the surface and return to the radar
receiver. By measuring the time it takes for the signal to return, the altimeter will determine the distance to the point
directly below the spacecraft, and SO will construct a topographic profile of the planet in much the same way that sonar
is used on board ships to profile the ocean floor. By mission's end, the Magellan altimeter experiment will have produced
a topographic map showing height variations as small as 30 meters (98 feet) for the entire mapped part of the planet.
Several additional types of information will be collected by Magellan. When the dish antenna is pointing down at
Venus, it will also be used to measure the amount of natural thermal emissions, from which temperature variations on
the planet's surface can be determined. Analysis of the way in which the radar signals are reflected will yield data on
the electrical conductivity and roughness of the Venusian surface.
After each mapping pass, the spacecraft will
recede from Venus and the tape recorders will be rewound in preparation for data transmission. Because the same
antenna used for mapping will also be used for radio communications, the spacecraft must reorient itself to point the
antenna toward Earth. The transmissions will be received by the large antennas of NASA's Deep Space Network located
at various sites around the world, then relayed to the Jet Propulsion Laboratory in Pasadena, California. While Magellan
is in radio communication with Earth, precise measurements can be made of the slight changes in the spacecraft's orbital
motions. These tiny motions, which are produced by variations in Venus' gravitational field, will provide important clues
about the nature of the planet's interior. After its "call home" is completed, the spacecraft will maneuver into position
to begin another mapping pass and will again point down toward the surface.
Since Venus will be rotating slowly
10
TEN
When Magellan's elliptical orbit
brings the spacecraft close to
the Venusian surface, the radar
instrument will look through the
clouds to map the solid planet.
Magellan will spend most of the rest of
its orbit transmitting data back to Earth.
beneath Magellan's orbit, the surface will be mapped in successive, slightly overlapping strips. Each strip, or swath, as
it is called, will be about 25 kilometers (16 miles) wide and about 16,000 kilometers (9,942 miles) long. Close to the
north pole, successive swaths will naturally converge, causing considerable overlapping. Since complete coverage of the
north pole can be obtained by using every other swath, an alternating pattern of northern and southern mapping passes
will be used. Thus, on one orbit, mapping will be performed from the north pole to a southern latitude for exactly 37.2
minutes. On the next orbit, mapping will start 4.7 minutes later than on the previous orbit and will stop 4.7 minutes farther
south.
Magellan's inclined orbit and its limited time for transmitting data to Earth make it impossible to obtain
full coverage of both poles during the course of one 243-day mapping cycle. Scientists and mission designers therefore
faced a difficult choice: whether to fully map the northern or the southern hemisphere. Because the large "continent"
of Ishtar, which extends into high northern latitudes, seems to have a number of significant geologic provinces, it was
decided to provide full coverage of the northern hemisphere.
Mapping of the low southern hemisphere, which does not
have as high a scientific priority, will extend to about 70 degrees south latitude.
Thus, eight times each day, for
243 days, Magellan will take radar images of the Venusian surface. At the end of the primary mission, almost 90 percent
of the planet will have been mapped. The image strips will be combined by computers on Earth into photomosaic images
covering large regions of the Venusian surface.
THE PLANET VENUS
Earth and Venus have many similar characteristics, such as size, density, and the presence of atmospheres. However,
they also show important differences. Although both planets are most likely made of the same type of silicate rock and
probably have similar interiors, Venus does not appear to have a magnetic field as Earth does. Venus is closer to the
12
TWELVE
Sweltering under a
perpetual cloud cover, Venus
reveals no surface details
even in ultraviolet light, but a
radar instrument on the Pioneer
Venus Orbiter revealed the large-scale
geography of the planet for the first time. Blue areas represent
the Venusian lowlands, while highlands
are shown in green, yellow, and red.
Sun than Earth and receives almost twice as much solar radiation. Although both planets have atmospheres, the Venusian
atmosphere is much denser than our own and is composed almost entirely of carbon dioxide, with a high-altitude covering
of clouds laced with sulfuric acid droplets. This thick atmospheric blanket of carbon dioxide traps outgoing thermal
radiation between the solid surface and the atmosphere. Far from being Earth's "twin" at the surface, Venus is a perpetual
furnace, where surface temperatures reach 480 degrees Celsius (900 degrees Fahrenheit) and the atmospheric pressure
is 90 times that of Earth. Any liquid water that might have once existed has long since disappeared: Venus today is bone-
dry.
We know some things about Venusian geology from past space probes and from Earth-based radar studies.
Soviet lander photos and chemical analysis experiments have shown that the rocks of the highland areas at the lander
sites are basaltic, like the rocks on Earth's ocean floor or the rocks that are formed from oozing volcanic lava flows.
Venus' large-scale geography has been disclosed by radar studies from Earth, by the Pioneer Venus Orbiter in 1978,
and by the Soviet Venera 15 and 16 missions in 1983. Most of the planet consists of either rolling upland plains
(apparently composed of older crustal rock) or smooth lowland areas. There are two major "continents," or elevated
plateaus-Aphrodite, named for the Greek equivalent of the goddess Venus, and Ishtar, named for the Babylonian
equivalent-that appear to be younger geologically. Ishtar is about the size of Australia; Aphrodite is about twice as large,
or approximately the same size as South America. Jutting up from the Ishtar highlands is one of the highest mountains
in the solar system, 10,800-meter-high (35,400-foot-high) Mount Maxwell. Two other highland areas of possible volcanic
and tectonic origin, Alpha Regio and Beta Regio, also stand out conspicuously.
14
FOURTEEN
A portion of the elevated
"continent" of Ishtar Terra
(about the size of
Australia) is shown in this
computer-processed
ISHTAR TERRA
Pioneer Venus image.
At the center is Mount
Lakshmi
Maxwell (also called
Colette
Mount Maxwell
Maxwell Montes), which is
10,800 meters (35,400 feet)
high, more than a mile
Ut Rupes
Vesta Rupes
taller than Mount Everest.
There is some evidence that
this buge mountain is an
active volcano. The
Lakshmi plateau, rising 4
to 5 kilometers (2.5 to 3.1
miles) above the mean level
of Venus, is bordered by
mountain ranges to the
north and northwest.
This plateau is thought to
consist of thin lavas
overlying an uplifted
section of older crust.
Soviet Venera radar data
suggest that the depression
called Colette is a collapsed
volcanic crater. On Ishtar's
southern flank are the Ut
and Vesta Rupes (cliffs),
Apbrodite Terra, Venus'
which descend to vast
largest elevated landmass
lowlands.
(about the size of South
America), bas two major
Diana Chasma
mountain regions on
opposite sides of the
"continent." Apbrodite
also bas the lowest
APHRODITE TERRA
elevations on Venus-in
the trenches of the Diana
Chasma, which may be a
rift valley caused by the
movement of two blocks
of crust away from each
other.
ARE EARTH AND VENUS TWINS?
Some 4.6 billion years ago, the planets of the solar system condensed as large, individual bodies in a whirlpool of solid
material and gas revolving around the Sun. Heavier elements like iron and silicon remained in the inner solar system
to form the rocky planets, Mercury, Venus, Earth, and Mars. The lighter gases-hydrogen and helium-went to form the
giant planets beyond the asteroid belt. The largest rocky planet, Earth, was extremely hot in those millennia after it
condensed into a solid sphere, and in its early history the planet released this heat through violent eruptions from great
volcanoes that covered its surface. Earth still sheds its heat today, but now as a low simmer, with only isolated chains
of volcanoes spewing hot material from its interior.
Earth's upper crust is divided into irregular, flat pieces-
tectonic plates-that move around the planet's surface, driven by convection cells in the hot, fluid rock underneath the
solid crust. Virtually all of Earth's large-scale geological features, including mountain chains and ocean basins, result
from the movement of these plates. When continental plates collide, mountains such as the Himalayas and the Alps are
thrust upward. Where the plates pull apart, rift valleys and ocean basins form. Earthquakes and volcanoes, the major
geologic upheavals on our planet, occur primarily at plate boundaries where pieces of the crust are stretching apart or
crunching together. One of the most important questions for the study of Venus is whether similar tectonic plate
movements have shaped the surface of our planetary "twin."
Although we might reasonably expect Earth's "twin"
to have similar processes shaping its surface, the limited data about Venus do not provide evidence of planetwide plate
tectonics. On Earth, where plates are pushing away from each other in the middle of the Atlantic Ocean, there is a
volcanic ridge thousands of miles in length where a great deal of the planet's internal heat is vented. No such conspicuous
plate boundaries appear in the Pioneer Venus Orbiter map, suggesting that if a system of plate tectonics does exist on
16
SIXTEEN
This glimpse of the Venusian surface
was taken by one of the Soviet
Venera landers. The reddish
appearance of the rocks is due to the
reddish color of the thick
atmosphere. The slabby rocks, which
are probably volcanic in origin,
would appear neutral gray in
natural sunlight. The rectangular
color bar at the bottom of the photo
is a part of the lander.
Venus, it must be of a different kind than Earth's. (However, evidence of plate tectonics, even on Earth, would only be
marginally visible at the image resolution of the Pioneer Venus Orbiter. Also, the Venera 15 and 16 coverage [25 percent
of the planet] may not be extensive enough to reveal a systematic, global pattern of plate tectonics.)
QUESTIONS FOR MAGELLAN'S EXPLORATION OF VENUS
Volcanoes
One of the most important tasks for Magellan during its mapping mission will be to take an inventory of volcanic craters
and other volcanic features on Venus SO that scientists can reconstruct the planet's geologic history. Ground-based and
Venera radar images have shown the existence of volcanic craters on the Ishtar plateau. Variations in the concentration
of sulfur dioxide in the atmosphere, detected by Pioneer Venus, suggest that Venus may be volcanically active. By
counting how many volcanoes are on Venus' surface and identifying where and what kind they are, Magellan will provide
data on the planet's internal processes.
The high-resolution radar images will allow us to discriminate between
individual overlapping lava flows SO as to determine the sequence of volcanic events that have helped shape the surface.
By examining the slopes and shapes of these volcanic flows, scientists can make judgments about the composition of the
lava and thus obtain further clues about the nature of the planet's interior and the thickness of the crust.
Earlier
spacecraft data have shown that the gravitational field of Venus is stronger over the planet's elevated plateaus-evidence
that these topographic features are related to the interior structure. Magellan's high-resolution gravity survey, constructed
by precise measurements of the spacecraft's orbital motions, will provide details about this important correlation between
gravity and topography.
18
EIGHTEEN
The improvement in resolution
expected from the Magellan data
is illustrated in these images of
the Mount Saint Helens region of
Washington, which are simulations
derived from the radar imaging data
acquired by the Seasat oceanographic
satellite. The still-active volcano does
not show at the Pioneer Venus resolution.
Although the feature is visible at the
Venera resolution, it is not possible to tell
whether it is a volcano or a meteorite
impact crater.
MAGELLAN
VENERA
PIONEER
Impact Craters
Meteorite impact craters also appear in abundance in radar images of Venus. Such craters are more plentiful than on
Earth, but much less SO than on Mercury, the Moon, and Mars. Another major task for Magellan will be to distinguish
these impact scars from volcanic craters, to count how many are still preserved on the surface, and to note where they
exist. It is important to establish Venus' impact cratering record, since the more cratered a surface is, the older it must
be. Earth's surface is relatively young-looking and uncratered. Although meteorites have struck our planet in the past,
most impact craters have been erased by wind and water erosion and by the constant motion of tectonic plates through
time. The surface of Earth is a slate that has been drawn on, wiped clean, redrawn, and rewiped over millions of
centuries. Venus, on the other hand, appears to retain evidence of a comparatively distant past. Magellan's global
inventory of impact craters will have much to tell scientists about the history of the planet and the ages of different
geologic provinces. The rate of surface cratering may also provide information on how dense the planet's atmosphere
has been through time.
At the best resolutions obtained to date, it is unclear whether many of the circular features
seen on Venus are the scars of old impacts, collapsed remnants of volcanic craters, or domes of rock somehow warped
upward by tectonic forces. Magellan's high-resolution radar images will clear up the mystery. If these images show large
stretches of old, cratered terrain, it would argue against tectonic motion in those regions, because crustal movements
would destroy old craters. It would also indicate that the processes of erosion proceed much more slowly on Venus than
on Earth.
20
TWENTY
This computer-generated photo shows that
only very general conclusions about the geology of a planet-
Venus or Earth-can be drawn from radar images
with the resolution obtained by Pioneer Venus. The images
from the bigher-resolution Magellan radar will give
scientists a better understanding of processes that have
shaped the Venusian surface and interior.
Faults, Ridges, and Mountains
Some kind of crustal movement evidently is at work on Venus, because mountain-like folded ridges and rift-like valleys
appear in Soviet radar images of Ishtar Terra. These features are most probably caused by the compression or extension
of the crust. Magellan will reveal the details of these features, allowing scientists to characterize how Venusian tectonics
work. It has been proposed that the high surface temperatures on Venus play a part in the distortion of the crust, and
Magellan will provide new data to test that theory. Large rift valleys such as Devana Chasma in Beta Regio will be studied
to see whether they were formed by volcanic processes or by tectonic motions.
Water and Wind
Another critical question about Venus is whether it once had water on its surface. Modern-day ratios of deuterium to
hydrogen in Venus' atmosphere (measured by descending atmospheric probes) suggest that at some point in the past there
was more water in the planet's atmosphere. Magellan will look for evidence of ancient marine terraces, river channels
and deltas, or other geologic features that might point to the existence of ancient oceans. Such discoveries would have
profound implications for the evolution of the planet's atmosphere as well as of its surface.
Although surface wind
speeds on Venus are believed to be lower than on Earth, there may be large windblown dunes on the surface that would
be evident in high-resolution Magellan images. The sizes and shapes of such dunes would allow scientists to reconstruct
the wind behavior on Venus.
22
TWENTY-TWO
During its primary 243-day mission,
Magellan will acquire more digital imaging
data than all previous U.S. planetary missions
combined. These data will be a legacy for future investigators of the veiled planet, just
as the findings from the expedition of
Ferdinand Magellan, the Project's namesake,
were for the then-future explorers of Earth.
T
he Soviet Venera 15 and 16
spacecraft mapped less than
one-third of the Venusian surface at
high resolution. Over the course of
one Venusian day (243 Earth days),
the Magellan spacecraft will map
most of the surface with detail that
exceeds that of these best previous
radar images. The resultant maps
will reveal the traces (if they exist) of
many fundamental planetary forces:
volcanism, wind, water, and
meteorite impacts-in short, all the
processes that determine a planet's
history and shape its face. By giving
us this new information, the Magellan
mission will help to tell us why
Venus, our planetary "twin," is at the
same time so much a stranger.
The International Science Team
Radar Investigation Group
Gordon H. Pettengill (Principal Investigator), Massachusetts Institute of Technology
Raymond E. Arvidson, Washington University
Victor R. Baker, University of Arizona
Joseph H. Binsack, Massachusetts Institute of Technology
Joseph M. Boyce, National Aeronautics and Space Administration
Donald B. Campbell, Cornell University
Merton E. Davies, RAND Corporation
Charles Elachi, Jet Propulsion Laboratory, California Institute of Technology
John E. Guest, University College London, England
James W. Head, III, Brown University
William M. Kaula, National Oceanographic and Atmospheric Administration
Kurt L. Lambeck, The Australian National University, Australia
Franz W. Leberl, Vexcel Corporation
Harold MacDonald, University of Arkansas
Harold Masursky, U.S. Geological Survey
Daniel P. McKenzie, Bullard Laboratories, England
Barry E. Parsons, University of Oxford, England
Roger J. Phillips, Southern Methodist University
R. Keith Raney, Canada Centre for Remote Sensing, Canada
R. Stephen Saunders, Jet Propulsion Laboratory, California Institute of Technology
Gerald Schaber, U.S. Geological Survey
Gerald Schubert, University of California, Los Angeles
Laurence A. Soderblom, U.S. Geological Survey
Sean C. Solomon, Massachusetts Institute of Technology
H. Ray Stanley, National Aeronautics and Space Administration
Manik Talwani, Geotechnology Research Institute
G. Leonard Tyler, Stanford University
John A. Wood, Smithsonian Astrophysical Observatory
Gravity Investigation Group
Michel Lefebvre (Principal Investigator), Centre National d'Etudes Spatiales, France
William L. Sjogren (Principal Investigator), Jet Propulsion Laboratory, California Institute of Technology
Mohan Ananda, Aerospace Corporation
Georges Balmino, Centre National d'Etudes Spatiales, France
Nicole Borderies, Centre National d'Etudes Spatiales, France
Bernard Moynot, Centre National d'Etudes Spatiales, France
NASA
National Aeronautics and
Space Administration
Jet Propulsion Laboratory
California Institute of Technology
Pasadena, California
JPL 400-345