Mars Reconnaissance Orbiter

has alleviated the issue. However, the cause is still unknown and may return. HiRISE was able to photograph the Phoenix lander during its parachuted descent to Vastitas Borealis on May 25, 2008 (sol ).

The orbiter continued to experience recurring problems in 2009, including four spontaneous resets, culminating in a four-month shut-down of the spacecraft from August to December.

On March 3, 2010, the MRO passed another significant milestone, having transmitted over 100 terabits of data back to Earth, which was more than all other interplanetary probes sent from Earth combined.

In December 2010, the first Extended Mission began. Goals included exploring seasonal processes, searching for surface changes, and providing support for other Martian spacecraft. This lasted until October 2012, after which NASA started the MRO<nowiki/>'s second Extended Mission, which lasted until October 2014.

On August 6, 2012 (sol ), the orbiter passed over Gale crater, the landing site of the Mars Science Laboratory mission, during its EDL phase. It captured an image via the HiRISE camera of the Curiosity rover descending with its backshell and supersonic parachute. In December 2014 and April 2015, Curiosity was photographed again by HiRISE inside Gale Crater.

Another computer anomaly occurred on March 9, 2014, when the MRO put itself into safe mode after an unscheduled swap from one computer to another. The MRO resumed normal science operations four days later. This occurred again on April 11, 2015, after which the MRO returned to full operational capabilities a week later. as well as the Mars Odyssey Orbiter and MAVEN orbiter had a chance to study the Comet Siding Spring flyby on October 19, 2014. To minimize risk of damage from the material shed by the comet, the MRO made orbital adjustments on July 2, 2014, and August 27, 2014. During the flyby, the MRO took the best ever pictures of a comet from the Oort cloud and was not damaged. In October 2016, the crash site of another lost spacecraft, Schiaparelli EDM, was photographed by the MRO, using both the CTX and HiRISE cameras. The maneuver's engine burn lasted for 75 seconds. InSight was delayed and missed the 2016 launch window, but was successfully launched during the next window on May 5, 2018, and landed on November 26, 2018.

Due to the longevity of the mission, a number of MRO components have started deteriorating. From the start of the mission in 2005 to 2017, the MRO had used a miniature inertial measurement unit (MIMU) for altitude and orientation control. After 58,000 hours of use, and limited signs of life, the orbiter switched over to a backup, which, as of 2018, has reached 52,000 hours of use. To conserve the life of the backup, NASA switched from MIMUs to an "all-stellar" mode for routine operations in 2018. The "all-stellar" mode uses cameras and pattern recognition software to determine the location of stars, which can then be used to identify the MRO<nowiki/>'s orientation. Problems with blurring in pictures from HiRISE and battery degradation also arose in 2017 but have since been resolved. In August 2023, electronic units within the HiRISE's CCD RED4 sensor began to fail as well, and are causing visual artifacts in pictures taken.

In 2017, the cryocoolers used by CRISM completed their lifecycle, limiting the instrument's capabilities to visible wavelengths, instead of its full wavelength range. In 2022, NASA announced the shutdown of CRISM in its entirety, and the instrument was formally retired on April 3, 2023, after creating two final, near global, maps using prior data and a more limited second spectrometer that did not require cryocoolers.

, the MRO has around 132 kg of fuel remaining, enough to support operations until 2035.

HiRISE

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

=== CTX ===

The Context Camera (CTX) provides grayscale images (500 to 800 nm) with a pixel resolution up to about . CTX is designed to provide context maps for the targeted observations of HiRISE and CRISM, and is also used to mosaic large areas of Mars, monitor a number of locations for changes over time, and to acquire stereo (3D) coverage of key regions and potential future landing sites.

MARCI

The Mars Color Imager (MARCI) is a wide-angle, relatively low-resolution camera that views the surface of Mars in five visible and two ultraviolet bands. Each day, MARCI collects about 84 images and produces a global map with pixel resolutions of . This map provides a weekly weather report for Mars, helps to characterize its seasonal and annual variations, and maps the presence of water vapor and ozone in its atmosphere. The same MARCI camera was onboard Mars Climate Orbiter launched in 1998.

CRISM

The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument is a visible and near infrared spectrometer that is used to produce detailed maps of the surface mineralogy of Mars. CRISM is being 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. The CRISM instrument was shut down on April 3, 2023.

MCS

The Mars Climate Sounder (MCS) is a radiometer that looks both down and horizontally through the atmosphere in order to quantify the atmosphere's vertical variations. It has one visible/near infrared channel (0.3 to 3.0 μm) and eight far infrared (12 to 50 μm) channels selected for the purpose. MCS observes 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 increments. These measurements are assembled into daily global weather maps to show the basic variables of Martian weather: temperature, pressure, humidity, and dust density. Since beginning operation, it has helped create maps of mesospheric clouds, study and categorize dust storms, and provide direct evidence of carbon dioxide snow on Mars.

This instrument, supplied by NASA's Jet Propulsion Laboratory (JPL), is an updated version of a heavier, larger instrument originally developed at JPL for the 1992 Mars Observer and 1998 Mars Climate Orbiter missions, which both failed.

SHARAD

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

The Shallow Radar (SHARAD) sounder experiment onboard MRO is designed to probe the internal structure of the Martian polar ice caps. It also gathers planet-wide information about underground layers of regolith, rock, and ice that might be accessible from the surface. SHARAD emits HF radio waves between 15 and 25 MHz, a range that allows it to resolve layers as thin as to a maximum depth of . It has a horizontal resolution of .

Engineering instruments and experiments

In addition to its imaging equipment, MRO carries three engineering instruments. The Electra communications package is a UHF software-defined radio that provides a flexible platform for evolving relay capabilities. It is 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 an ultra-stable oscillator. Doppler information for approaching vehicles can be used for final descent targeting or descent and landing trajectory recreation. Doppler information on landed vehicles allows scientists to accurately determine the surface location of Mars landers and rovers. The two Mars Exploration Rover (MER) spacecraft utilized an earlier generation UHF relay radio providing similar functions through the Mars Odyssey orbiter. The Electra radio has relayed information to and from the MER spacecraft, Phoenix lander and Curiosity rover.

thumb|An image of [[Phobos (moon)|Phobos taken by HiRISE on March 23, 2008, from a distance of around ]]

During the cruise phase, the MRO also used the Telecommunications Experiment Package to demonstrate a less power-intensive way to communicate with Earth.

The Optical Navigation Camera images the Martian moons, Phobos and Deimos, against background stars to precisely determine MRO<nowiki/>'s orbit. Although this is not critical, it was included as a technology test for future orbiting and landing of spacecraft.

Spacecraft systems

thumb|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, and Malin Space Science Systems in San Diego. The spacecraft's total mass is less than with an unfueled dry mass less than . Along with the Electra communications package, the system consists of a very large () High Gain Antenna, which is used to transmit data to the Deep Space Network on Earth via X-band frequencies at 8.41 GHz. It also demonstrates the use of the Ka band at 32 GHz for higher data rates. Maximum transmission speed from Mars can be as high as 6 Mbit/s, but averages between 0.5 and 4 Mbit/s.

Two smaller low-gain antennas are also present for lower-rate communication during emergencies and special events. 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 was used to show how such a system could be used by spacecraft in the future. 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) implemented Ka-band receiving capabilities at all three of its complexes (Goldstone, Canberra and Madrid) over its 34-m beam-waveguide (BWG) antenna subnet.thumb|High-resolution image of [[Victoria (crater)|Victoria crater from HiRISE on October 3, 2006. The rover Opportunity can be seen at roughly the "ten o'clock" position along the rim of the crater.]]

Propulsion and attitude control

The spacecraft uses a fuel tank filled with of hydrazine monopropellant. Fuel pressure is regulated by adding pressurized helium gas from an external tank. Seventy percent of the propellant was used for orbital insertion,

MRO has 20 rocket engine thrusters on board. Six large thrusters each produce of thrust for a total of meant mainly for orbital insertion. These thrusters were originally designed for the Mars Surveyor 2001 Lander. Six medium thrusters each produce of thrust for trajectory correction maneuvers and attitude control during orbit insertion. Finally, eight small thrusters each produce of thrust for attitude control during normal operations.

In order to determine the spacecraft's orbit and facilitate maneuvers, 16 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, measures changes to the spacecraft attitude as well as any non-gravitationally 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.

Cost

thumb|MRO development and prime mission costs, by fiscal year

The total cost of the MRO through the end of its prime mission was . Of this amount, was spent on spacecraft development, approximately for its launch, and for 5 years of mission operations. Since 2011, MRO<nowiki/>'s annual operations costs are, on average, per year, when adjusted for inflation. The MRO<nowiki/>'s science budget has, like other long term missions, been declining, leading to reduced science activity. SHARAD has provided strong evidence that the LDAs in Hellas Planitia are glaciers that are covered with a thin layer of debris (i.e. rocks and dust); a strong reflection from the top and base of LDAs was observed, suggesting that pure water ice makes up the bulk of the formation (between the two reflections).

Chloride deposits and aqueous minerals

thumb|Chloride deposits in Terra Sirenum|209x209px

Using data from Mars Global Surveyor, Mars Odyssey, and the MRO, scientists have found widespread deposits of chloride minerals. Evidence suggests that the deposits were formed from the evaporation of mineral enriched waters. The research suggests that lakes may have been scattered over large areas of the Martian surface. Usually, chlorides are the last minerals to come out of solution. Carbonates, sulfates, and silica should precipitate out ahead of them. Sulfates and silica have been found by the Mars rovers on the surface. Places with chloride minerals may have once held various life forms. Furthermore, such areas could preserve traces of ancient life. In 2017, however, further research suggested that the dark streaks were created by grains of sand and dust slipping down slopes, and not water darkening the ground.

Notes

References

External links

Official instrument websites

HiRISE website from The University of Arizona
CTX website from Malin Space Science Systems
MARCI website from Malin Space Science Systems
SHARAD website from NASA
CRISM website from Johns Hopkins University Applied Physics Laboratory

Images

MRO images at the JPL Photojournal
MRO images at the NASA Image Gallery