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NASA’s OSIRIS-REx spacecraft moved within about 131 feet, or 40 meters, of asteroid Bennu this week in the last practice of the $ 1 billion mission, before a touch-and-go landing on the asteroid in October was to collect monsters for return to Earth.
During Tuesday’s sampling rehearsal, engineers controlling Earth’s spacecraft maneuvers confirmed that navigation algorithms, autonomous operations software, scientific instruments, and various mechanical systems all worked as expected.
On Tuesday, the OSIRIS-REx spacecraft fired thrusters to leave a “safe home orbit” roughly 0.6 miles (1 kilometer) from the asteroid Bennu, and then descended to a point about 125 meters (125 meters) above it. surface of the asteroid. The spaceship then fired thrusters to carry out a so-called “checkpoint” fire to initiate a free fall to the asteroid.
Eight minutes later, OSIRIS-REx pulsed its control jets again for a “matchpoint” fire to deal with the motion of the spacecraft with the rotation of the asteroid. This allows the spacecraft to make its final descent to the surface over the intended sampling location.
The spaceship continued to descend after the fire from the matchpoint three minutes after the asteroid, reaching a point 131 meters from Bennu before firing thrusters again for a maneuver back.
The position OSIRIS-REx reached at Tuesday’s rehearsal marked the closest the spacecraft has come to asteroid Bennu, after a similar sampling exercise in April that increased the mission’s distance maneuvers to a point 213 feet, or 65 meters, from the asteroid.
After launching Earth in 2016 and reaching its asteroid target in 2018, NASA’s Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer, or OSIRIS-REx, Spacecraft Bennu mapped with cameras, mineral sniffing spectrometers and a Canadian laser built to measure its roughness.
Shaped like a revolving top, Bennu measures approximately 1,614 feet (492 meters) wide. At the time of Tuesday’s rehearsal, the asteroid was approximately 179 million miles (288 million kilometers) from Earth. At that distance, it takes 16 minutes for ground team commands to reach the OSIRIS-REx spacecraft.
“This time lapse prevented live command of ground-level flight activities during the rehearsal,” NASA said in a statement. “As a result, the spacecraft performed the entire rehearsal game autonomously.”
Ground controllers linked the origin sequence in advance to the spacecraft in time, and OSIRIS-REx flew the origin profile on autopilot, just as it will be on the actual sample.
OSIRIS-REx visited sites for its sample collection, but scientists discovered that Bennu is rougher than expected.
The spaceflight sampling rehearsal focused Tuesday on a location called Nightingale, the mission’s primary sample storage located within a 140-meter (140-meter) crater in the northern hemisphere of Bennu. The site is surrounded by boulders and sharp terrain, forcing engineers to develop upgraded navigation capabilities to guide the spacecraft itself to a safe approach-and-go landing.
OSIRIS-REx uses a feature called natural function tracking to take a series of images with a navigation camera to autonomously identify rocks, craters and other markings on the surface of the asteroid, and provide position and relative velocity data. The spaceship’s computer compares the image with a map of dangers loaded before the arrival in the computer. If OSIRIS-REx detects that it is approaching a dangerous area, it may be a short cut and run back from Bennu.
The algorithms for tracking natural functions were successfully tested during Tuesday’s rehearsal. The spacecraft’s cameras captured higher-resolution views of the Nightingale sampling location as OSIRIS-REx flew directly over the site, allowing ground crews to update and refine their natural feature tracking capabilities before attempting actual sampling in October.
“Many important systems were practiced during this rehearsal – from communications, spaceships, and most importantly, the on-board natural function to tracking and hazard tracking,” said Dante Lauretta, OSIRIS-REx’s lead researcher at the University of Arizona, Tucson. “Now that we’ve completed this milestone, we are confident in finalizing the procedures for the TAG (Touch-And-Go) event. This rehearsal confirmed that the team and all spaceship systems are ready to collect a sample in October. ”
OSIRIS-REx also extended its sample collection arm, known as TAGSAM, during Tuesday’s rehearsal. The spacecraft also moved its two wings of solar array to a “Y-wing” configuration to place them safely away from the asteroid’s surface, just as they will be placed during the on-and-off landing. .
The TAGSAM arm was later retracted to a stowed position after OSIRIS-REx began flying away from Bennu at the end of the rehearsal Tuesday.
During the actual sampling run of the mission, a device mounted at the end of the TAGSAM spacecraft arm will contact the asteroid and compressed nitrogen gas fire for several seconds. The gas cartridge will disrupt the rock at the sampling site, and the spacecraft will trap some of the material in a room before returning to Earth.
Scientists hope to collect at least 2.1 ounces (60 grams) of resulting samples from Bennu’s surface, and return the Earth to Earth in September 2023 for analysis in similar laboratories. Scientists will examine the specimens to look for signs of organic matter and other chemicals that are critical to the origin of life.
Built and operated by Lockheed Martin, the OSIRIS-REx spacecraft launched from Cape Canaveral in September 2016. A limited number of personnel on Tuesday managed to control the control point of a Lockheed Martin control center in Colorado, plus seats at the Goddard Space Flight Center in Maryland and the University of Arizona.
Other team members have participated remotely because of the coronavirus pandemic, NASA said.
Earlier this year, mission managers decided to give teams more time to prepare for the OSIRIS-REx sample as officials adapt to new operational schemes to minimize COVID-19 risks.
That decision delayed the second rehearsal of OSIRIS-REx from June 23 to August 11, and postponed the actual sampling run from August 25 to October 20.
When the first sample rises low in October, scientists have made pencils in chances for extra threads before the spaceship Bennu departs next year to begin its return trip to Earth.
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