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Mars Reconnaissance Orbiter

2007 Schools Wikipedia Selection. Related subjects: Space transport

   Mars Reconnaissance Orbiter
   Conceptual drawing of Mars Reconnaissance Orbiter over Mars
   Organization: NASA
   Major Contractors: Lockheed Martin Space Systems, University of
   Arizona, Johns Hopkins University Applied Physics Laboratory, Italian
   Space Agency, Malin Space Science Systems, JPL
   Mission type: Orbiter
   Satellite of: Mars
   Orbital Insertion date: March 10, 2006
   Launch Date: August 12, 2005
   Launch Vehicle: Atlas V-401 rocket
   Mission Duration: 4 years
   NSSDC ID: 2005-029A
   Webpage: Mars Reconnaissance Orbiter
   Mass: 2,180 kg (4,806 lb) with fuel
   Power: Two solar panels, 2,000 watts

   NASA's Mars Reconnaissance Orbiter (MRO) is a multipurpose spacecraft
   designed to conduct reconnaissance and exploration of Mars from orbit.
   The $720 million USD spacecraft was built by Lockheed Martin under the
   supervision of the Jet Propulsion Laboratory. It was launched August
   12, 2005 and attained Martian orbit on March 10, 2006. It has recently
   finished aerobraking, and entered its final science orbit. It is
   expected to begin its primary science phase in November 2006.

   MRO contains a host of scientific instruments such as cameras,
   spectrometers, and RADAR, which will be used to analyze the landforms,
   stratigraphy, minerals, and ice of Mars. It will pave the way for
   future spacecraft by monitoring daily weather and surface conditions,
   studying potential landing sites, and testing a new telecommunications
   system. MRO's telecommunications system will transfer more data back to
   Earth than all previous interplanetary missions combined, and MRO will
   serve as a highly capable relay satellite for future missions.

   MRO joins four other spacecraft currently studying Mars: Mars Express,
   Mars Odyssey, and two Mars Exploration Rovers. This is the largest
   number of active spacecraft to study another planet at the same time in
   the history of space exploration.

Prior to launch

   Mars Surveyor Orbiter, an orbiting satellite whose hallmark was a
   high-resolution camera, was first proposed to NASA in 1999. It was one
   of two missions being considered for the 2003 launch opportunity;
   however, during the proposal process the orbiter competed and lost
   against what became known as the Mars Exploration Rovers. The orbiter
   mission was rescheduled for launch in 2005, and NASA announced its
   final name, Mars Reconnaissance Orbiter, on October 26, 2000..

   MRO was modeled after NASA's highly successful Mars Global Surveyor to
   conduct surveillance of Mars from orbit. Early specifications of the
   satellite included a large camera to take high resolution pictures of
   Mars. In this regard, Jim Garvin, the Mars exploration program
   scientist for NASA, proclaimed that MRO would be a "microscope in
   orbit". The satellite was also to include a visible-near-infrared
   spectrograph.

   On October 3, 2001, NASA chose Lockheed Martin as the primary
   contractor for the spacecraft's fabrication. By the end of 2001 all of
   the mission's instruments were selected. There were no major setbacks
   during MRO's construction, and the spacecraft was moved to John F.
   Kennedy Space Centre on May 1, 2005 to prepare it for launch.

Launch and orbital insertion

   Launch of Atlas V carrying the Mars Reconnaissance Orbiter, 11:43:00
   UTC August 12, 2005
   Enlarge
   Launch of Atlas V carrying the Mars Reconnaissance Orbiter, 11:43:00
   UTC August 12, 2005

   On August 12, 2005, MRO was launched aboard an Atlas V-401 rocket from
   Space Launch Complex 41 at Cape Canaveral Air Force Station. The
   Centaur upper stage of the rocket completed its burns over a fifty-six
   minute period and placed MRO in interplanetary transfer orbit towards
   Mars.

   MRO cruised through interplanetary space for 7.5 months before reaching
   Mars, and most of the scientific instruments and experiments were
   tested and calibrated en route. To ensure proper orbital insertion upon
   reaching Mars, four trajectory correction maneuvers were planned and a
   fifth emergency maneuver was discussed. However, only three trajectory
   correction maneuvers were necessary, saving fuel for MRO's extended
   mission.

   MRO began orbital insertion by approaching Mars on March 10, 2006 and
   passing above its southern hemisphere at an altitude of 370–400 km
   (190 mi). All six of MRO's main engines burned for 27 minutes to slow
   the probe from ~2,900 m/s to ~1,900 m/s (6,500 mph to 4,250 mph). The
   helium pressurization tank was colder than expected, which reduced the
   pressure in the fuel tank by about 21  kPa (3  psi). The reduced
   pressure caused the engine thrust to be diminished by 2%, but MRO
   automatically compensated by extending the burn time by 33 seconds.
   Artwork of MRO aerobraking
   Enlarge
   Artwork of MRO aerobraking

   Orbital insertion placed the orbiter in a highly elliptical polar orbit
   with a period of approximately 35.5 hours. Shortly after insertion, the
   periapsis — the point in the orbit closest to Mars — was 3,806 km from
   the planet's centre (426 km from its surface). The apoapsis — the point
   in the orbit farthest from Mars — was 47,972 km from the planet's
   centre (44,500 km from its surface).

   On March 30, 2006, MRO began the process of aerobraking, a three-step
   procedure that cuts in half the fuel needed to achieve a lower, more
   circular orbit with a shorter period. First, during its first five
   orbits of the planet (one Earth week), MRO used its thrusters to drop
   the periapsis of its orbit into aerobraking altitude. This altitude
   depends on the thickness of the atmosphere because Martian atmospheric
   density changes with its seasons. Second, while using its thrusters to
   make minor corrections to its periapsis altitude, MRO maintained
   aerobraking altitude for 445 planetary orbits (about 5 Earth months) to
   reduce the apoapsis of the orbit to 450 km (280 mi). This was done in
   such a way so as to not heat the spacecraft too much, but also dip
   enough into the atmosphere to slow the spacecraft down. After the
   process was complete, MRO used its thrusters to move its periapsis out
   of the edge of the Martian atmosphere, August 30, 2006.

   In September of 2006 MRO fired its thrusters twice more to fine-tune
   its final, nearly circular orbit approximately 250 to 316 km (155 to
   196 mi) above the Martian surface. The SHARAD dipole antenna were
   deployed the September 16. All of the scientific instruments will be
   tested and most were turned off prior to the solar conjunction which
   occurred from October 7, 2006 to November 6, 2006. The "primary science
   phase" began after the conjunction ended.

   On November 17, 2006 NASA announced the successful test of the MRO as
   an orbital communications relay. Using the NASA rover " Spirit" as the
   point of origin for the transmission, the MRO acted as a relay for
   transmitting data back to Earth.

Mission objectives

   Science instrumentation of MRO
   Enlarge
   Science instrumentation of MRO

   Beginning in November 2006, MRO will conduct science operations for two
   Earth years. One of the mission's main goals is to map the Martian
   landscape with high-resolution cameras in order to choose other landing
   sites for future missions. These include the Phoenix Lander, which will
   explore the Martian Arctic, and the Mars Science Laboratory, a highly
   maneuverable rover. MRO will help planners evaluate both the scientific
   value and the landing risks for possible landing sites for these
   missions. It will also provide a transmission relay and critical
   navigation data during their landing.

   MRO will also use its on-board scientific equipment to study the
   Martian climate, weather, atmosphere, and geology, and to search for
   signs of water in the polar caps and underground. In addition, MRO will
   look for the remains of the previously lost Mars Polar Lander and
   Beagle 2 spacecraft, and will serve as the first step in setting up an
   internet protocol for the different planets in our solar system. After
   its main science operations are completed, the probe's extended mission
   will continue using the communication and navigation system for future
   lander and rover probes.

Events and discoveries

   The first image by the HiRISE camera shows the Ius Chasma section of
   the Valles Marineris system of canyons.
   Enlarge
   The first image by the HiRISE camera shows the Ius Chasma section of
   the Valles Marineris system of canyons.

   On September 29, 2006, MRO took its first high resolution image from it
   science orbit. This image is said to resolve items as small as
   armchairs on the surface (90 cm (3 feet) in diameter).

   On October 6, 2006, NASA released detailed pictures from the MRO of
   Mars' Victoria Crater along with the Opportunity rover on the rim above
   it.

Instruments

   Six science instruments are included on the mission along with two
   "science-facility instruments", which use data from engineering
   subsystems to collect science data. Three technology experiments will
   test and demonstrate new equipment for future missions.

HiRISE

   HiRISE camera structure
   Enlarge
   HiRISE camera structure

   The High Resolution Imaging Science Experiment camera is a 0.5 m
   reflecting telescope, the largest ever carried on a deep space mission,
   and has a resolution of 1 microradian (μrad), or 0.3 m from an altitude
   of 300 km. In comparison, satellite images of Earth are generally
   available with a resolution of 0.1 m, and satellite images on Google
   Maps are available to 1 m. HiRISE collects images in three colour
   bands, 400 to 600 nm ( blue- green or B-G), 550 to 850  nm ( red) and
   800 to 1,000 nm ( near infrared or NIR).

   Red colour images are 20,264 pixels across (6 km wide), and B-G and NIR
   are 4,048 pixels across (1.2 km wide). HiRISE's on-board computer reads
   these lines in time with the orbiter's ground speed, and images are
   potentially unlimited in length. Practically however, their length is
   limited by the computer's 28 Gigabit (Gb) memory capacity, and the
   nominal maximum size is 20,000 × 40,000 pixels (800 megapixels) and
   4,000 × 40,000 pixels (160 megapixels) for B-G and NIR images. Each
   16.4 Gb image will be compressed to 5 Gb before transmission and
   released to the general public on the HiRISE website in JPEG 2000
   format. To facilitate the mapping of potential landing sites, HiRISE
   can produce stereo pairs of images from which topography can be
   calculated to an accuracy of 0.25 m. HiRISE was built by Ball Aerospace
   & Technologies Corp.

CTX

   The Context Imager (CTX) provides grayscale images (500 to 800 nm) up
   to 40 km wide with a pixel resolution of 6 m. The CTX is designed to
   provide context maps for the targeted observations of HiRISE and CRISM.
   The optics of CTX consist of a 350 mm focal length Maksutov Cassegrain
   telescope with a 5,064 pixel wide line array CCD similar to the HiRISE
   instrument. The instrument will take pictures 30 km (19 mi) wide and
   has enough internal memory to store an image 160 km long before loading
   it into the main computer.

MARCI

   Mars Color Imager
   Enlarge
   Mars Colour Imager

   The Mars Colour Imager (MARCI) is a wide-angle, low-resolution camera
   that views the surface of Mars in five visible and two ultraviolet
   bands. Each day, MARCI will collect about 84 images and produce a
   global map with pixel resolutions of 1 to 10 km. This map will provide
   a daily weather report for Mars, help to characterize its seasonal and
   annual variations, and map the presence of water vapor and ozone in its
   atmosphere.

CRISM

   CRISM Instrument
   Enlarge
   CRISM Instrument

   The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM)
   instrument is a visible and near infrared (VNIR) spectrometer that will
   produce detailed maps of the surface mineralogy of Mars. It operates
   from 370 to 3920 nm, measures the spectrum in 544 channels (each
   6.55 nm wide), and has a resolution of 18 m at an altitude of 300 km.
   CRISM will be used to identify minerals and chemicals indicative of the
   past or present existence of water on the surface of Mars. These
   materials include iron, oxides, phyllosilicates, and carbonates, which
   have characteristic patterns in their visible-infrared energy.

MCS

   The Mars Climate Sounder (MCS) is a spectrometer with one visible/near
   infrared channel (0.3 to 3.0 μm) and eight far infrared (12 to 50 μm)
   channels. These channels were selected to measure temperature,
   pressure, water vapor and dust levels. MCS will observe the atmosphere
   on the horizon of Mars (as viewed from MRO) by breaking it up into
   vertical slices and taking measurements within each slice in 5 km
   (3 mi) increments. These measurements will be assembled into daily
   global weather maps to show the basic variables of Martian weather:
   temperature, pressure, humidity and dust density.

SHARAD

   An artist's concept of MRO using SHARAD to "look" under the surface of
   Mars
   Enlarge
   An artist's concept of MRO using SHARAD to "look" under the surface of
   Mars

   MRO's Shallow Subsurface Radar (SHARAD) experiment is designed to probe
   the internal structure of the Martian polar ice caps. It will also
   gather planet-wide information about underground layers of ice, rock
   and possibly liquid water that might be accessible from the surface.
   SHARAD uses HF radio waves between 15 and 25  MHz, a range that allows
   it to resolve layers as thin as 7 m to a maximum depth of 1 km. It will
   have a horizontal resolution as high as 0.3 by 3 km. SHARAD is designed
   to operate in conjunction with Mars Express's MARSIS, which has lower
   resolution but penetrates to a much greater depth. Both SHARAD and
   MARSIS were made by the Italian Space Agency.

Engineering instruments

   In addition to its imaging equipment, MRO will carry a variety of
   engineering instruments. The Gravity Field Investigation Package will
   measure variations in the Martian gravitational field through
   variations in the spacecraft's velocity. Velocity changes are detected
   by measuring doppler shifts in MRO's radio signals received on Earth.
   The package also includes sensitive on-board accelerometers used to
   deduce the in situ atmospheric density of Mars during aerobraking.

   The Electra is a UHF software defined radio designed to communicate
   with other spacecraft as they approach, land, and operate on Mars. In
   addition to protocol controlled inter-spacecraft data links of 1 kbit/s
   to 2 Mbit/s, Electra also provides Doppler data collection, open loop
   recording and a highly accurate timing service based on a 5e-13 USO.
   Doppler information for approaching vehicles can be used for final
   descent targeting or descent and landing trajectory recreation. Doppler
   informaion on landed vehicles will also enable scientists to accurately
   determine the surface location of Mars landers and rovers. The two MER
   spacecraft currently on Mars utilize an earlier generation UHF relay
   radio providing similar functions through the Mars Odyssey orbiter. The
   Electra radio may use the MER spacecraft to prove its functionality but
   it is not scheduled to provide formal relay services until the 2008
   arrival of the Phoenix Mars lander. Because the Electra radio is
   software defined down to the modem level, new modulation, coding or
   protocol functions can be added or updated while the MRO spacecraft is
   in orbit around Mars.

   The Optical Navigation Camera images the Martian moons, Phobos and
   Deimos, against background stars to precisely determine MRO's orbit.
   Although moon imaging is not mission critical, it was included as a
   technology test for future orbiting and landing of spacecraft. The
   Optical Navigation Camera was tested successfully in February and March
   of 2006.

Engineering data

   Size comparison of MRO with predecessors
   Enlarge
   Size comparison of MRO with predecessors

Structure

   Workers at Lockheed Martin Space Systems in Denver assembled the
   spacecraft structure and attached the instruments. Instruments were
   constructed at the Jet Propulsion Laboratory, the University of Arizona
   Lunar and Planetary Laboratory in Tucson, Arizona, Johns Hopkins
   University Applied Physics Laboratory in Laurel, Maryland, the Italian
   Space Agency in Rome, Italy, and Malin Space Science Systems in San
   Diego, California. The total cost of the spacecraft was $720 million
   USD.

   The structure is made of mostly carbon composites and
   aluminium-honeycombed plates. The titanium fuel tank takes up most of
   the volume and mass of the spacecraft and provides most of its
   structural integrity. The spacecraft's total mass is less than 2,180
   kg (4,806  lb) with an unfueled dry mass less than 1,031 kg (2,273 lb).

Power systems

   Mars Reconnaissance Orbiter's solar panel
   Enlarge
   Mars Reconnaissance Orbiter's solar panel

   MRO gets all of its electrical power from two solar panels, each of
   which can move independently around two axes (up-down, or left-right
   rotation). Each solar panel measures 5.35 × 2.53 m and has 9.5 m²
   (102 ft²) covered with 3,744 individual photovoltaic cells. Its
   high-efficiency triple junction solar cells are able to convert more
   than 26% of the sun's energy directly into electricity and are
   connected together to produce a total output of 32  volts. At Mars, the
   two panels produce 2,000 watts of power; in contrast, the panels would
   generate 6,000 watts in a comparable Earth orbit by being closer to the
   Sun.

   MRO has two nickel metal hydride rechargeable batteries used to power
   the spacecraft when it is not facing the sun. Each battery has an
   energy storage capacity of 50  ampere-hours (180  kC). The full range
   of the batteries cannot be used due to voltage constraints on the
   spacecraft, but it will allow the operators to extend the battery
   life—a valuable capability, given that battery drain is one of the most
   common causes of long-term satellite failure. Planners anticipate that
   only 40% of the batteries' capacities will be required during the
   lifetime of the spacecraft.

Electronic systems

   MRO‘s main computer is a 133  MHz, 10.4 million transistor, 32-bit,
   RAD750 processor. This processor is a radiation-hardened version of a
   PowerPC 750 or G3 processor with a specially-built motherboard. The
   RAD750 is a successor to the RAD6000. This processor may seem
   underpowered in comparison to a modern PC or Mac processor, but it is
   extremely reliable, resilient, and can function in solar flare-ravaged
   deep space. The operating system software is VxWorks and has extensive
   fault protection protocols and monitoring.

   Data is stored in a 160  Gb (20  GB) flash memory module consisting of
   over 700 memory chips, each with a 256  Mbit capacity. This memory
   capacity is not actually that large considering the amount of data to
   be acquired; for example, a single image from the HiRISE camera can be
   as large as 28 Gb.

Attitude determination

   In order to determine the spacecraft's orbit and facilitate maneuvers,
   sixteen sun sensors — eight primaries and eight backups — are placed
   around the spacecraft to calibrate solar direction relative to the
   orbiter's frame. Two star trackers, digital cameras used to map the
   position of catalogued stars, provide NASA with full, three-axis
   knowledge of the spacecraft orientation and attitude. A primary and
   backup Miniature Inertial Measurement Unit (MIMU), provided by
   Honeywell, will measure changes to the spacecraft attitude as well as
   any non-gravitionally induced changes to its linear velocity. Each MIMU
   is a combination of three accelerometers and three ring-laser
   gyroscopes. These systems are all critically important to MRO, as it
   must be able to point its camera to a very high precision in order to
   take the high-quality pictures that the mission requires. It has also
   been specifically designed to minimize any vibrations on the
   spacecraft, so as to allow its instruments to take images without any
   distortions caused by vibrations.

Telecommunications system

   MRO High Gain Antenna installation
   Enlarge
   MRO High Gain Antenna installation

   The Telecom Subsystem on MRO is the best telecom system sent into deep
   space so far. It consists of a very large (3 meter) antenna, which will
   be used to transmit data through the Deep Space Network via X-band
   frequencies at 8  GHz, and it will demonstrate the use of the Ka-band
   at 32 GHz for higher data rates. Maximum transmission speed from Mars
   is projected to be as high as 6 Mbit/s, a rate ten times higher than
   previous Mars orbiters. The spacecraft carries two 100-watt X-band
   amplifiers (one of which is a backup), one 35-watt Ka-band amplifier,
   and two transponders.

   Two smaller low-gain antennas are also present for lower-rate
   communication during emergencies and special events, such as launch and
   Mars Orbit Insertion. These antennas do not have focusing dishes and
   can transmit and receive from any direction. They are an important
   backup system to ensure that MRO can always be reached, even if its
   main antenna is pointed away from the Earth.

   The Ka-band subsystem is used for demonstration purposes. Due to lack
   of spectrum at 8.41 GHz X-band, future high-rate deep space missions
   will use 32 GHz Ka-band. NASA Deep Space Network (DSN) has implemented
   Ka-band receiving capabilities at all three of its complexes
   (Goldstone, Canberra and Madrid) over its 34-m beam-waveguide (BWG)
   antenna subnet. MRO Ka-band demonstration will demonstrate viability of
   Ka-band for deep space operations. During the cruise phase, spacecraft
   Ka-band telemetry was tracked 36 times by these antennas proving DSN
   Ka-band reception functionality at all the antennas. During the primary
   science phase, Ka-band demonstration will be assigned two passes a week
   for Ka-band demonstration purposes. The success of Ka-band during
   cruise also makes it a viable backup for the X-band subsystem on MRO.

Propulsion and attitude control

   Data comparison chart
   Enlarge
   Data comparison chart

   The spacecraft uses a 1175  L (310 US gal) fuel tank filled with
   1187 kg (2617 lb) of hydrazine monopropellant. Fuel pressure is
   regulated by adding pressurized helium gas from an external tank.
   Seventy percent of the fuel will be used for orbital insertion.

   MRO has twenty rocket engine thrusters on board. Six large thrusters
   each produce 170  N (38  lbf) of thrust for a total of 1,020 N
   (230 lbf) meant mainly for orbital insertion. These thrusters were
   originally designed for the Mars Surveyor 2001 Lander. Six medium
   thrusters each produce 22 N (5 lbf) of thrust for trajectory correction
   maneuvers and attitude control during orbit insertion. Finally, eight
   small thrusters each produce 0.9 N (0.2 lbf) of thrust for attitude
   control during normal operations.

   Four reaction wheels are also used for precise attitude control during
   activities requiring a highly stable platform, such as high-resolution
   imaging, in which even small motions can cause blurring of the image.
   Each wheel is used for one axis of motion. The fourth (skewed) wheel is
   a backup in case one of the other three wheels fails. Each wheel weighs
   10 kg (22 lb) and can be spun as fast as 100 Hz or 6,000  rpm.

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