Eleven years into its mission, the Lunar Reconnaissance Orbiter (LRO) is beginning to show its age, but a recent software update promises to give the spacecraft new life. As NASA’s eye was in the sky over the moon, the LRO was responsible for some of the best lunar observations since the days of Apollo. With this new upgrade, the legacy can continue.
Launched in June 2009, the LRO has quickly managed to map more than 98% of the moon’s surface with a resolution of 100 meters per pixel. The orbit is also known for taking incredible high-resolution images of the Apollo landing sites, in which landers, robbers, tire tracks and astronaut footprints are clearly visible.
In 2016, the LRO found evidence that the moon is geologically active due to tidal forces from the earth, and also because the moon shrinks as its core cools. More recently, the LRO was able to observe the impact sites of both the Vikram Lander of the Indian Space Research Organization and the Beresheet Lander of SpaceIL (both impressive and record-breaking missions, despite their ‘explosive’ endings).
However, the monumental record of the LRO did not make it immune to problems. The misery began in 2018, when the LRO’s aging miniature inertia unit (MIMU), a tool used to measure the rotation of the spacecraft, had to shut down. Without the MIMU, the LRO only has to rely on star trackers to orient itself. Star detection is a perfectly viable alternative for the MIMU, by using star positions such as a map to tell the spacecraft in which direction it is facing.
Without new software, however, the star tracking method prevented the LRO from making the quick, intricate maneuvers needed to take angular images of the Moon. These side shots are important for two reasons. The first is that they allowed photometry, or the ability to examine how the brightness of the surface changes from different perspectives. Second, it offers the ability to produce spectacular 3D images, giving the geographical features of the moon a sense of depth and realism, which is sometimes lacking in the map-like images created by shooting straight.
The LRO team had to write a new algorithm, which they called ‘FastMan’, the abbreviation for ‘Fast Maneuver’ to increase the LRO’s ability to reorient quickly for sideways shots. It was first brought online in 2020 and has been a huge success so far.
One of the challenges FastMan had to overcome was that if the star trackers were accidentally shown on a bright object such as the sun, moon or earth, they would lose their ability to orient the spacecraft. FastMan ensures that this does not happen.
Initially, FastMan required off-ground input to work with the flight software, but it is now integrated so that FastMan can perform sideways maneuvers autonomously.
With the upgrade installed, the LRO will continue to do science for the next decade. On the lifespan of the LRO going forward, Noah Petro, project scientist for LRO at NASA Goddard, said that “fuel could be our rate-limiting factor, according to current estimates we should still have at least five years of fuel on board, if not more.”
Although the LRO has exceeded its initial mission objectives, the continued well-being of the spacecraft in the coming years will continue to be an asset, not least because it will be able to support the Artemis program, which is underway to: human lunar landing to reach somewhere this decade. Long live the LRO!
More info: Bill Steigerwald, “Teach an old spacecraft new tricks to explore the moon,” GSFC.