NASA tests out thrusters on OSIRIS-REx; slightly adjusts spacecraft’s trajectory

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The Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx) spacecraft is well on its way towards the asteroid Bennu from which it intends to extract a sample and return to Earth in 2023. While the launch was spot-on, NASA recently tested out the thrusters on OSIRIS-REx just to ensure that things are all good and slightly adjust the spacecraft’s trajectory.

NASA revealed that they had planned to fire the Trajectory Correction Maneuver (TCM) thrusters aboard the spacecraft soon after its launch, but the launch of OSIRIS-REx was almost perfect that left no room for any deviation in the spacecraft’s trajectory. Because of this instead of the original plan of burning 388 ounces (11 kilograms) of propellant to create a velocity change of up to 26 miles per hour (11.6 meters per second), the mission team had to burn only 18 ounces (.5 kilogram) of fuel changing velocity of the OSIRIS-Rex spacecraft by 1.1 mile per hour (50 centimeters per second) in 12 seconds. The spacecraft is currently about 9 million miles (14.5 million kilometers) from Earth.

Read: OSIRIS-Rex mission to asteroid Bennu will see UBC team lend ‘geo-expertise’ to NASA

The October 7 maneuver was rather a test of the TCM thrusters and a practice for the mission team for possibly much larger burns scheduled in December and possibly more such burns in the future as the spacecraft draws much closer to the asteroid. Because NASA saved a whole lot of propellant thanks to the accurate launch, the propellant will be useful for the spacecraft’s asteroid proximity operations once OSIRIS-REx arrives at Bennu.

To track the maneuver, the OSIRIS-REx mission’s navigation team monitored the Doppler shift in radio signals between the spacecraft and the Deep Space Network antenna at the Goldstone Observatory in California. After 44 seconds—the current one-way light time delay between the spacecraft and Earth—the team received the first maneuver data from the spacecraft. Over the next week, the navigation team will process daily spacecraft tracking data to determine the precise effect of the burn.

The OSIRIS-REx spacecraft has four different kinds of thrusters providing considerable redundancy in its ability to maneuver on its way to the surface of Bennu and back. OSIRIS-REx began using its Attitude Control System (ACS) thrusters shortly after launch to keep the spacecraft oriented, so that its solar arrays point toward the sun and its communication antennas point toward Earth.

The TCM-1 used the larger Trajectory Correction Maneuver (TCM) thrusters. In December OSIRIS-REx will use its largest thrusters, the Main Engine (ME) thrusters, to target the spacecraft for its Earth Gravity Assist scheduled for Sept. 22, 2017. Its smallest thrusters, the Low Thrust Reaction Engine Assembly (LTR) thrusters, will be used for the delicate maneuvers close to the surface of the asteroid Bennu.



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