Richard Leis

Orbit Obtained: MRO Makes it to Mars

Mars Reconnaissance Orbiter (MRO) performed a flawless engine burn today in a successful bid to enter orbit around Mars. The event, known as Mars Orbital Insertion (MOI), is a risky one for robotic visitors to the Red Planet. Now that MRO is safely in orbit, the spacecraft will soon begin several months of aerobraking to reshape the orbit into a circle approximately 300 km above the martian surface. The primary science phase of the mission will begin in the fall after aerobraking has been completed.

At the University of Arizona, an audience of students, the public, reporters, and other guests watched live NASA TV coverage of the event. The High Resolution Imaging Science Experiment (HiRISE) camera is one of the instruments on board MRO and is operated by a team at the University of Arizona. HiRISE Principal Investigator Alfred McEwen and operations team members were on hand for presentations, narration of the television coverage, and answers to audience questions. [Disclosure: Richard Leis is a HiRISE operations team member.]

The risks of any orbital insertion include missing the target altogether or coming in too closely. During MRO MOI, all predicted events occurred on schedule, including the loss of signal from the spacecraft while it passed behind Mars. Reacquisition of the signal from MRO occurred at around 3:15 pm Mountain Standard time, and a few minutes later flight operations at the Jet Propulsion Laboratory in Pasadena, California, USA confirmed that the spacecraft was in the correct initial orbit around Mars. The audience and HiRISE team applauded and cheered the successful conclusion of each major event.

MRO launched from Cape Canaveral in Florida, USA on August 12, 2005. During its 7 month cruise to Mars, instruments on board were turned on and tested in preparation for future science gathering. HiRISE, for example, snapped high resolution images of the moon and stellar clusters. These images are now being used by the operations team to calibration the instrument and develop imaging processing software and procedures.

MRO will remain in its current orbit for about two weeks prior to the start of aerobraking. During that two weeks, some of the operations teams for the various instruments will again turn on their instruments. HiRISE will take nine images of Mars and once again the operations team will use these images for further calibration and testing.

Aerobraking occurs when MRO dips down into the martian atmosphere to create friction that helps slow down the spacecraft and lower its orbit. The process will take from five to seven months depending on the condition of the martian atmosphere on any given day.

After aerobraking, MRO will into a transition orbit during which time the instrument teams will complete their preparations for the primary science phase of the mission. Know as PSP, this phase of the mission will last for two years while scientific data is gathered.

The HiRISE camera is the largest such device ever sent outside the Earth’s orbit. The camera will capture high resolution images of the martian surface, up to 20,000 by 60,000 pixels in size. These images are so huge that they will not fit full size on a regular computer monitor. Only a display array of 20 by 60 monitors would have enough pixels available to show one full-sized HiRISE image. Because of this, recent compression and delivery technology known as JPEG2000 is being used to allow the scientific community and the public to browse through these images over the internet.

At its best setting, HiRISE will be able to see objects roughly one meter (approximately one yard) in size. Meanwhile, two other cameras will take lower resolution images but provide more coverage of the planet. Together, these cameras should reveal a different Mars than shown by previous orbiters, simply because so much more detail and wider coverage will become available than ever before. In fact, so much data will be obtained during the course of the mission that it will dwarf what many previous missions have obtained, combined.

MRO is also equipped with a sounding radar called SHARAD (Shallow Radar) which will return the highest resolution data of the martian subsurface. In recent years, previous spacecraft have detected the presence of water deposits beneath the surface of Mars. SHARAD will attempt to better quantify the amount of water present and in what form – ice or liquid – it exists.

Scientists hope to learn where the water believed to have existed on early Mars went, in what form it exists today, and if water might still flow on the surface (as appears to be the case with gullies discovered by previous spacecraft.) They also hope to learn more about the martian atmosphere and surface history. The information obtained could help determine whether or not Mars has ever been hospitable to life and which locations are best to search for fossil or current lifeforms.

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Richard Leis

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