Instrument Host Overview
Mars Reconnaissance Orbiter Spacecraft
Mars Reconnaissance Orbiter uses a spacecraft design provided by
Lockheed Martin Space Systems that is smarter, more reliable, more
agile, and more productive than any previous Mars orbiter. It is
the first spacecraft designed from the ground up for aerobraking,
a rigorous phase of the mission where the orbiter uses the
friction of the martian atmosphere to slow down in order to settle
into its final orbit around Mars.
When fully assembled and fueled, the spacecraft had to weigh less
than 2,180 kilograms (4,806 pounds) so that the Atlas V launch
vehicle could lift it into the proper orbit. All subsystems and
instruments on board (the so-called 'dry mass') weighed less than
1,031 kilograms (2,273 pounds) to allow room for 1,149 kilograms
(2,533 pounds) of propellant for trajectory correction maneuvers
that kept the spacecraft on target during the cruise to Mars and
for burns that helped capture the spacecraft into orbit around
During its five-year mission, the spacecraft needed to operate in
four distinct mission phases.
Launch: During launch, the spacecraft had to fit within the nose
cone, or payload fairing, of the launch vehicle, so the large
parts like the high-gain antenna and the solar arrays were
designed to be folded up. As soon as the launch vehicle placed the
spacecraft on a course to leave earth orbit for its journey to
Mars, it disconnected itself from the spacecraft.
Cruise: As soon as the spacecraft was clear of the launch vehicle,
the orbiter deployed its solar arrays to begin producing power.
The high-gain antenna was also be deployed at this point. The
high-gain antenna moved to track the Earth, while the solar panels
Mars Orbit Insertion and Aerobraking: The Mars orbit insertion and
aerobraking configuration looked very much like the cruise
configuration, except that the high-gain antenna was moved to a
position that balanced the solar arrays as it flew through the
upper atmosphere of Mars. The heaviest part of the spacecraft (the
propellant tank) also made the spacecraft very stable. Due to the
large area (37.7 square meters or 405.8 square feet) of the
spacecraft in this configuration, each pass through the martian
atmosphere during aerobraking caused significant slowing, thus
reducing the size of the orbit. Friction from the atmosphere had
the additional effect of heating up the spacecraft, so components
were designed to withstand this heating. The flight team could
further control the heating by changing how deeply the spacecraft
dipped into the atmosphere on each orbit.
Science Operations: During the primary science phase, the
orbiter's job was to point its science instruments at Mars to
collect images and other data from targets on the surface of Mars,
while ensuring that the high-gain antenna and solar arrays were
continuously tracking the Earth and the Sun, respectively.
The orbiter typically kept its science instruments pointed to
nadir (looking straight down at the surface). A few times per day,
and for about fifteen minutes each time, the orbiter pointed side-
to-side in order to capture high-priority science targets that did
not fall directly beneath the spacecraft. The spacecraft could
point off-nadir up to 30 degrees.
Major Spacecraft Components
Science Payload Instruments: To fulfill the mission science
objectives, seven scientific investigations teams were selected by
NASA. Four teams (MARCI, MCS, HiRISE, and CRISM) were led by
Principal Investigators (PI). Each PI lead team was responsible
for the provision and operation of a scientific instrument and the
analysis of its data. The PI lead investigations were: Mars Color
Imager (MARCI); Mars Climate Sounder, (MCS); High Resolution
Imaging Science Experiment, (HiRISE); and Compact Reconnaissance
Imaging Spectrometer for Mars, (CRISM).
In addition to the PI lead teams, there were two investigation
teams that made use of facility instruments. The facility
instruments were Context Imager (CTX) and Shallow (Subsurface)
The MARCI PI and Science Team also acted as Team Leader (TL) and
Team Members for the CTX facility instrument. The Italian
Space Agency (ASI) provided a second facility instrument, SHARAD,
for flight on MRO. ASI and NASA both selected members of the
SHARAD investigation team with ASI appointing the Team Leader and
NASA appointing the Deputy Team Leader.
In addition to the instrument investigations, Gravity Science and
Atmospheric Structure Facility Investigation Teams used data from
the spacecraft telecommunications and accelerometers,
respectively, to conduct scientific investigations.
The science instruments are summarized below.
Instrument: CRISM (Compact Reconnaissance Imaging Spectrometer for
Type: High-Resolution Imaging Spectrometer
Measurements: Hyper-spectral Image Cubes, 514 spectral bands,
0.4-4 microns, 7 nm resolution, from 300km; 20 m/pixel, 11 km
Science Goals: Regional & local surface composition and morphology.
Key Attributes: Moderately high spectral & spatial resolution,
targeted and regional survey, very high data rate.
Principal Investigator: Scott Murchie, Johns Hopkins University
Applied Physics Lab.
Instrument: CTX (Context Imager)
Type: Mono-chromatic Context Camera
Measurements: Panchromatic (minus blue)Images from 300km
altitude; 30km swath & 6m/pixel context imaging for HiRISE/CRISM
& MRO science.
Science Goals: Regional stratigraphy and morphology.
Key Attributes: Moderately high resolution with coverage, targeted
& regional survey; high data rate.
Team Leader: Michael Malin, Malin Space Science Systems (MSSS).
Instrument: HiRISE (High Resolution Imaging Science Experiment)
Type: High-Resolution Camera (0.5 m aperture)
Measurements: Color images, stereo by site revisit, from
300km; < 1m/pixel (ground sampling @ 0.3 m/pixel), 6 km swath in
red (broadband), 1.2km swath in blue-green & NIR.
Science Goals: Stratigraphy, geologic processes and morphology.
Key Attributes: Very high resolution targeted imaging, very high
Principal Investigator: Alfred McEwen, University of Arizona.
Instrument: MARCI (Mars Color Imager)
Type: Wide-Angle Color Imager
Measurements: Coverage of atmospheric clouds, hazes and ozone,
and surface albedo in 7 color bands (0.28-0.8 micrometers)
(2 UV, 5 Visible).
Science Goals: Global weather and surface change.
Key Attributes: Daily global coverage daily global mapping,
continuous operations dayside; moderate data rate.
Principal Investigator: Michael Malin, Malin Space Science Systems
Type: Atmospheric Sounder
Measurements: Atmospheric profiles of water, dust, co2 &
temperature, polar radiation balance, 0-80km vertical coverage,
vertical resolution ~5km.
Science Goals: Atmospheric structure, transport and polar processes.
Key Attributes: Global limb sounding; daily, global limb &
on-planet mapping; continuous operations day and night; low data
Principal Investigator: Originally Daniel J. McCleese, Jet Propulsion
Lab (JPL); currently David Kass, JPL.
Type: Shallow Subsurface Radar Sounder
Measurements: Ground penetrating radar; 10-MHz band centered at
20 MHz; 15 m free space vertical resolution; 1.5-8 km horizontal
resolution, improved to 0.3-1 km along-track with SAR processing.
Science Goals: Regional near-surface ground structure.
Key Attributes: Shallow sounding; regional profiling; high data
Team Leader: Roberto Seu, University of Rome, Italy.
Deputy Team Leader: To 2015: Roger Phillips, Washington University,
St. Louis, and Southwest Research Institute; From 2015: Nathaniel
Putzig, Planetary Science Institute.
Engineering Instruments: Mars Reconnaissance Orbiter carried three
instruments that will assist in spacecraft navigation and
1. Electra UHF Communications and Navigation Package: Electra
allowed the spacecraft to act as a communications relay between
the Earth and landed crafts on Mars that may not have sufficient
radio power to communicate directly with Earth by themselves.
2. Optical Navigation Camera: This camera was being tested for
improved navigation capability for future missions. Similar
cameras placed on orbiters of the future would be able to serve as
high-precision interplanetary 'eyes' to guide incoming spacecraft
as they near Mars.
3. Ka-band Telecommunications Experiment Package: Mars
Reconnaissance Orbiter tested the use of a radio frequency
called Ka-band to demonstrate the potential for greater
performance in communications using significantly less power.
Structures: The structures subsystem is the skeleton around which
the spacecraft was assembled. It supported and protected the other
engineering subsystems and the science instruments. It was strong
enough to survive launch, when the forces can exceed 5 g's.
Extremely lightweight but strong materials were used to achieve
this strength, including titanium, carbon composites, and aluminum
Mechanisms: There were three main mechanisms on board Mars
* one that allowed the high-gain antenna to move in order to point
* two that allowed the solar arrays to move to point at the sun
Each of these mechanisms, called gimbals, moved about two axes in
much the same way that your wrist allows your hand to move in two
axes: left/right and up/down.
As the spacecraft traveled around Mars each orbit, these gimbals
allowed both solar arrays to be always pointed toward the sun,
while the high-gain antenna could simultaneously always be pointed
Telecommunications System: The telecommunications subsystem was a
two-way radio system used for receiving and transmitting commands
and data between the Mars Reconnaissance Orbiter and the Deep
Space Network antenna on earth. With its large-dish antenna,
powerful amplifier, and fast computer, Mars Reconnaissance Orbiter
could transmit data to earth at rates as high as 6 megabits per
second, a rate ten times higher than previous Mars orbiters. The
orbiter's radio operated in the X-band of the radio spectrum, at a
frequency of around 8 Gigahertz.
Major components of the telecom subsystem included:
* Antennas for transmitting and receiving commands
* Amplifiers for boosting the power of radio signals so that they
are strong enough to be received at the Deep Space Network
* Transponders for translating navigation and other signals from
Also on board was Electra, a UHF telecommunications package that
was one of the engineering instruments providing navigation and
communications support to landers and rovers on the surface of
Mars. Electra allowed the spacecraft to act as a relay between the
earth and landed crafts on Mars, which may not have sufficient
radio power to communicate directly with earth.
High-gain Antenna: The high-gain antenna is a 3-meter diameter
(10-foot) dish antenna for sending and receiving data at high
rates. The high-gain antenna was deployed shortly after launch and
remained deployed for the remainder of the mission. It served as
the primary means of communication to and from the orbiter. The
high-gain antenna had to be pointed accurately and was therefore
steered using the gimbal mechanism.
Low-gain Antennas: Two smaller antennas were present for lower-
rate communication during emergencies and special events, such as
launch and Mars Orbit Insertion. The data rate of these antennas
was lower because they focused the radio beam much more broadly
than the high gain antenna, so less of the signal reached earth.
But the Deep Space Network station on the earth could detect the
signal even when the spacecraft was not pointed at earth, and
therefore these antennas were useful for emergencies. The low-gain
antennas had the capability to transmit and receive. The two low-
gain antennas were mounted on the high-gain antenna dish--one on
the front side and one on the back--and were moved with it. Two
were needed in that placement so that communication was possible
at all times, no matter what the position of the spacecraft might
be at a given time.
Amplifiers: Located on the backside of the high-gain antenna was
the enclosure for the Traveling Wave Tube Amplifiers, which
boosted the power of radio signals so that they were strong enough
to be received at the Deep Space Network antennas. There were
three amplifiers on board:
* two for the X-band radio frequency that transmitted radio
signals at a power of 100 watts (the second one was for back up
to ensure communications in case the first amplifier failed)
* one for Ka-band radio frequency that was capable of transmitting
at 35 watts.
Transponders: Mars Reconnaissance Orbiter carried two
transponders, which are special types of radio
receiver/transmitters, specially designed for long-range space
communications. The second transponder was a backup. The
transponders had several functions:
* transmit/receive function: translated digital electrical signals
into radio signals for sending data to earth, and translated radio
signals to digital electrical signals for receiving commands from
* transponding function: listened for and detected a signal coming
in from earth, to which it automatically responded
* navigation function: transmitted several types of signals that
provided critical navigation clues, enabling navigators on the
ground to make precise calculations of the spacecraft speed and
distance from earth
Propulsion: The propulsion subsystem performed major maneuvers
such as trajectory correction maneuvers and Mars orbit insertion.
The propulsion subsystem was also used to control the spacecraft's
position, as a backup to the reaction wheels.
Mars Reconnaissance Orbiter used a monopropellant propulsion
system: it carried fuel (hydrazine), but no oxidizer. Thrust was
produced by passing the fuel over beds of catalyst material just
before it entered the thruster, which caused the hydrazine to
The propulsion system included:
The monopropellant hydrazine tank held 1187 kilograms (2617
pounds) of usable propellant. Over 70% of the total propellant was
used during Mars orbit insertion.
Mars Reconnaissance Orbiter fed pressurized helium gas from a
separate high- pressure tank, through a regulator, into the
propellant tank where it put the hydrazine propellant under
Lines, Valves, and Regulators
The pressurized hydrazine flowed through a system of metal tubing
to each of the thrusters. Each thruster had a valve so that it
could be fired independently. Additional valves in the propellant
lines turned on and off the flow to groups of thrusters.
A total of 20 rocket engine thrusters were onboard:
* Six large thrusters, each producing 170 Newtons* (38 pounds
force) of thrust for performing the Mars orbit insertion burn.
Together, all six produce 1,020 Newtons (230 pounds force) of
* Six medium thrusters, each producing 22 Newtons* (5 pounds
force) of thrust for performing trajectory correction maneuvers,
and for helping to keep the spacecraft pointing in the right
direction during the Mars orbit insertion burn.
* Eight small thrusters, each producing 0.9 Newtons* (0.2 pounds
force) of thrust for controlling where the orbiter is pointed
during normal operations as well as during Mars orbit insertion
and trajectory correction maneuvers.
Command and Data-Handling Systems: The Command and Data Handling
subsystem controlled all spacecraft functions. This system:
* managed all forms of data on the spacecraft;
* carried out commands sent from earth;
* prepared data for transmission to the earth;
* managed collection of solar power and charging of the batteries;
* collected and processed information about all subsystems and
* kept and distributed the spacecraft time;
* calculated its position in orbit around Mars;
* carried out commanded maneuvers; and
* autonomously monitored and responded to any onboard
problems that occurred.
The key parts of this system were:
* Space Flight Computer (a space-qualified processor based on the
133 MHz PowerPC processor)
* Flight Software
* Solid State Recorder (total capacity 160 Gigabits)
Guidance, Navigation, and Control Systems: The guidance,
navigation, and control subsystem was used to control the
orientation of the orbiter as it travels through space and to
maintain knowledge of where celestial bodies are located (for
example, Earth and the sun). This knowledge was critical for the
spacecraft to perform the correct maneuvers to get to Mars, to
keep its solar arrays pointed toward the sun in order to produce
power, and to keep its antenna pointed toward the earth in order
to maintain communications.
Once in orbit around Mars, this subsystem also maintained constant
knowledge of where the spacecraft was in its orbit, and was able to
point the science cameras to an accuracy of about 1/20th of one
Electrical Power: The electrical power subsystem was responsible
for generating, storing, and distributing power to the orbiter
systems and included two solar panels and two nickel-hydrogen
Solar panels: The one and only source of power for Mars
Reconnaissance Orbiter was sunlight. Mounted on opposite sides of
the orbiter and capable of changing position to allow the orbiter
to track the sun continuously, each solar panel had an area of
approximately 10 square meters (107.6 square feet), and contained
3,744 individual solar cells. The solar cells were able to convert
more than 26% of the sun's energy directly into electricity. The
solar panels were deployed soon after launch and remained deployed
throughout the mission.
During aerobraking the solar panels had a special role to play. As
the spacecraft skimmed through the upper layers of the martian
atmosphere, the large, flat panels acted to slow the spacecraft
down and reduce the size of its orbit. The solar arrays were
designed to withstand temperatures of almost 200 Celsius.
Nickel-hydrogen batteries: Mars Reconnaissance Orbiter used two
nickel-hydrogen rechargeable batteries, each with an energy
storage capacity of 50 ampere-hours (at 32 volts, 1600 watts per
hour). Only about 40% of the battery capacity was intended to be
used. The batteries charged during the day side of each two-hour
orbit around Mars, using electricity produced by the solar cells,
and provided power during the night side of each orbit.
Thermal Systems: The thermal subsystem maintained the right
temperatures in all parts of the spacecraft. It employed several
conduction- and radiation-based techniques for thermal control:
* Surface coatings
* Thermal blankets