The Mars Reconnaissance Orbiter (MRO) is a spacecraft designed to search for the existence of water on Mars and provide support for missions to Mars, as part of NASA's Mars Exploration Program. It was launched from Cape Canaveral on August 12, 2005, at 11:43 UTC and reached Mars on March 10, 2006, at 21:24 UTC. In November 2006, after six months of aerobraking, it entered its final science orbit and began its primary science phase.
Mission objectives include observing the climate of Mars, investigating geologic forces, providing reconnaissance of future landing sites, and relaying data from surface missions back to Earth. To support these objectives, the MRO carries different scientific instruments, including three cameras, two spectrometers and a subsurface radar. , the MRO has returned over 450 terabits of data, helped choose safe landing sites for NASA's Mars landers, and discovered pure water ice in new craters and further evidence that water once flowed on the surface on Mars.
The spacecraft continues to operate at Mars, far beyond its intended design life. Due to its critical role as a high-speed data-relay for ground missions, NASA intends to continue the mission as long as possible, at least through the late 2020s. As of , , the MRO has been active at Mars for sols, or , and is the third longest-lived spacecraft to orbit Mars, after 2001 Mars Odyssey and Mars Express.
Pre-launch After the failures of the Mars Climate Orbiter and the Mars Polar Lander missions in 1999, NASA reorganized and replanned its Mars Exploration Program. In October 2000, NASA announced its reformulated Mars plans, which reduced the number of planned missions and introduced a new theme, "follow the water". The plans included the Mars Reconnaissance Orbiter (MRO), to be launched in 2005.
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 the MRO's construction, and the spacecraft arrived at John F. Kennedy Space Center on April 30, 2005, for launch preparations.
Mission objectives
MRO has both scientific and "mission support" objectives which were carried out during the mission's phases. The Primary Science Phase lasted until November 2008, at which time NASA declared the mission a success. The Extended Science Phase, lasting from 2008 to 2010, was initially planned to support the Phoenix lander and the Mars Science Laboratory, but they were uncontactable and delayed respectively, freeing up the MRO to further study Mars.After 2010, the mission consisted of Extended Mission (EM) phases, each lasting two years up to EM4, and three years from then on. As of 2024, the MRO is on its 6th extended mission.
The formal science objectives of MRO are to observe the present climate, particularly its atmospheric circulation and seasonal variations; search for signs of water, both past and present, and understand how it altered the planet's surface; map and characterize the geological forces that shaped the surface.
To support other missions to Mars, the MRO also has mission support objectives. They are to provide data relay services from ground missions back to Earth, characterize the safety and feasibility of potential future landing sites and Mars rover traverses, and capture data from the entry, descent and landing phase of rovers.
MRO played a key role in choosing safe landing sites for the Phoenix lander in 2008, Mars Science Laboratory / Curiosity rover in 2012, InSight lander in 2018, and the Mars 2020 / Perseverance rover in 2021.
Launch and orbital insertion
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 56-minute period and placed MRO into an interplanetary transfer orbit towards Mars.
MRO cruised through interplanetary space for seven and a half months before reaching Mars. While en route, most of the scientific instruments and experiments were tested and calibrated. 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, which saved of fuel that would be usable during 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 . All six of MRO's main engines burned for 27 minutes to slow the probe by . The burn was remarkably accurate, as the insertion route had been designed more than three months prior, with the achieved change in speed only 0.01% short from the design, necessitating an additional 35-second burn time.
Completion of the 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 from the surface ( from the planet's center). The apoapsis – the point in the orbit farthest from Mars – was from the surface ( from the planet's center).
When MRO entered orbit, it joined five other active spacecraft that were either in orbit or on the planet's surface: Mars Global Surveyor, Mars Express, 2001 Mars Odyssey, and the two Mars Exploration Rovers (Spirit and Opportunity). This set a new record for the most operational spacecraft in the immediate vicinity of Mars.
On March 30, 2006, MRO began the process of aerobraking, a three-step procedure that halved 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. Second, while using its thrusters to make minor corrections to its periapsis altitude, MRO maintained aerobraking altitude for 445 planetary orbits (about five Earth months) to reduce the apoapsis of the orbit to . 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. Third, after the process was complete, MRO used its thrusters to move its periapsis out of the edge of the atmosphere on August 30, 2006.
In September 2006, MRO fired its thrusters twice more to adjust its final, nearly circular orbit to approximately above the surface, with a period of about 112 minutes and a polar inclination of around 93°. The SHARAD radar antennas were deployed on September 16. All of the scientific instruments were tested and most were turned off prior to the solar conjunction that occurred from October 7 to November 6, 2006. This was done to prevent charged particles from the Sun from interfering with signals and potentially endangering the spacecraft. After the conjunction ended the "primary science phase" began.
Timeline
On September 29, 2006 (sol ), MRO took its first high resolution image from its science orbit. This image is said to resolve items as small as 90 cm (3 feet) in diameter. On October 6, NASA released detailed pictures from the MRO of Victoria crater along with the Opportunity rover on the rim above it. In November, problems began to surface in the operation of two MRO spacecraft instruments. A stepping mechanism in the Mars Climate Sounder (MCS) skipped on multiple occasions resulting in a field of view that was slightly out of position. By December, normal operations of the instrument had been suspended, although a mitigation strategy allows the instrument to continue making most of its intended observations. Also, an increase in noise and resulting bad pixels has been observed in several CCDs of the High Resolution Imaging Science Experiment (HiRISE). Operation of this camera with a longer warm-up time has alleviated the issue. However, the cause is still unknown and may return.
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. 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. Though engineers were not able to determine the cause of the recurrent resets, they suspected a piece of electronics had been affected by radiation. While investigating, the engineers discovered and fixed a flaw that could have deleted all critical information onboard the MRO. Another spontaneous reset occurred in September 2010.
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's second Extended Mission, which lasted until October 2014. As of 2023, the MRO has completed five missions, and is currently on its sixth.
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.
NASA reported that the MRO, 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 January 2015, the MRO discovered and identified the wreckage of Britain's Beagle 2, which was lost during its landing phase in 2003 and was thought to have crashed. The images revealed that Beagle 2 had actually landed safely, but one or two of its solar panels had failed to fully deploy, which blocked the radio antenna. In October 2016, the crash site of another lost spacecraft, Schiaparelli EDM, was photographed by the MRO, using both the CTX and HiRISE cameras.
On July 29, 2015, the MRO was placed into a new orbit to provide communications support during the anticipated arrival of the InSight Mars lander mission in September 2016. 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.