22.10.2020
OSIRIS-REx TAGs Surface of Asteroid Bennu
Captured on Oct. 20, 2020 during the OSIRIS-REx mission’s Touch-And-Go (TAG) sample collection event, this series of images shows the SamCam imager’s field of view as the NASA spacecraft approaches and touches down on asteroid Bennu’s surface, over 200 million miles (321 million km) away from Earth. The sampling event brought the spacecraft all the way down to sample site Nightingale, touching down within three feet (one meter) of the targeted location. The team on Earth received confirmation at 6:08 p.m. EDT that successful touchdown occurred. Preliminary data show the one-foot-wide (0.3-meter-wide) sampling head touched Bennu’s surface for approximately 6 seconds, after which the spacecraft performed a back-away burn.
The spacecraft’s sampling arm – called the Touch-And-Go Sample Acquisition Mechanism (TAGSAM) – is visible in the lower part of the frame. The round head at the end of TAGSAM is the only part of OSIRIS-REx that contacted the surface during the sample collection event. In the middle of the image sequence, the sampling head positions itself to contact the asteroid’s surface head-on. Shortly after, the sampling head impacts site Nightingale and penetrates Bennu’s regolith. Upon initial contact, the TAGSAM head appears to crush some of the porous rocks underneath it. One second later, the spacecraft fires a nitrogen gas bottle, which mobilizes a substantial amount of the sample site’s material. Preliminary data show the spacecraft spent approximately 5 of the 6 seconds of contact collecting surface material, and the majority of sample collection occurred within the first 3 seconds.
The TAGSAM is designed to catch the agitated surface material, and the mission team will assess the amount of material collected through various spacecraft activities. After touchdown, the spacecraft fired its thrusters to back away from Bennu. As expected, this maneuver also disturbed the Nightingale site, and loose debris is visible near the end of the image sequence. Preliminary telemetry shows the spacecraft remains in good health. The spacecraft was traveling at 0.2 mph (10 cm/sec) when it contacted sample site Nightingale and then backed away at 0.9 mph (40 cm/sec).
These images were captured over approximately a five-minute period. The imaging sequence begins at about 82 feet (25 meters) above the surface, and runs through the back-away maneuver, with the last image in the sequence taken at approximately 43 feet (13 meters) in altitude – about 35 seconds after backing away. The sequence was created using 82 SamCam images, with 1.25 seconds between frames. For context, the images are oriented with Bennu’s west at the top.
Quelle: NASA
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Update: 24.10.2020
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NASA: OSIRIS-REx successfully grabs asteroid Bennu sample, but too much
NASA's far-flung OSIRIS-REx spacecraft was successful in its mission to collect a sample from asteroid Bennu, the agency said Friday – but perhaps too successful.
Using a pogo stick-like device with a container, the spacecraft on Tuesday made contact with the asteroid and collected potentially hundreds of grams of material, far more than the originally planned 60 grams, or 2.1 ounces. But newly released images show the container's "lid" slightly stuck open due to the overflow, allowing some sample particles to escape into space.
NASA, University of Arizona, and Lockheed Martin teams would normally have spent Saturday measuring the size of the sample. But because the spacecraft clearly obtained far more than planned and some is actively being lost, NASA's science chief said Friday he decided to bypass the procedure and begin stowing as soon as possible.
"There is so much in there that the diaphragm that was supposed keep the sample in is stuck open," Thomas Zurbuchen said during a teleconference with reporters. "We observed some of the sample pieces escaping into space. Now time is of the essence."
If teams and the spacecraft are ready, Zurbuchen said, the 20-foot OSIRIS-REx will start the stowing process as soon as Monday, which is about two weeks earlier than planned.
"There's definitely evidence of hundreds of grams of material," said Dante Lauretta of the University of Arizona, the project's principal investigator. "We're concerned that the sample mass measurement planned for tomorrow would impart additional forces and actually cause us to lose mass."
"We're almost the victims of our own success here," he said.
If all goes well with the stowing process, OSIRIS-REx, now 200 million miles away from Earth, should depart the asteroid next spring. Its sample collection container is scheduled to land in Utah in September 2023.
Scientists ultimately hope to study the samples to obtain a better idea of how the solar system formed. Unusually dark and carbon-rich, Bennu is believed to harbor discoveries that could help with the understanding of life on Earth, too.
OSIRIS-REx, launched on a United Launch Alliance Atlas V rocket from Cape Canaveral in 2016, is NASA's first attempt at asteroid sample collection. Japan became the first country to pull off the maneuver in 2010 when its Hayabusa spacecraft successfully returned a sample from asteroid Itokawa.
If OSIRIS-REx's sample comes back safely, scientists hope to combine data from the Itokawa samples with those obtained from Bennu to magnify their findings.
Quelle: Florida Today
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Two days after touching down on asteroid Bennu, NASA’s OSIRIS-REx mission team received on Thursday, Oct. 22, images that confirm the spacecraft has collected more than enough material to meet one of its main mission requirements – acquiring at least 2 ounces (60 grams) of the asteroid’s surface material.
The spacecraft captured images of the sample collector head as it moved through several different positions. In reviewing these images, the OSIRIS-REx team noticed both that the head appeared to be full of asteroid particles, and that some of these particles appeared to be escaping slowly from the sample collector, called the Touch-And-Go Sample Acquisition Mechanism (TAGSAM) head. They suspect bits of material are passing through small gaps where a mylar flap – the collector’s “lid” – is slightly wedged open by larger rocks.
“Bennu continues to surprise us with great science and also throwing a few curveballs,” said Thomas Zurbuchen, NASA’s associate administrator for science at the agency’s headquarters in Washington. “And although we may have to move more quickly to stow the sample, it’s not a bad problem to have. We are so excited to see what appears to be an abundant sample that will inspire science for decades beyond this historic moment.”
The team believes it has collected a sufficient sample and is on a path to stow the sample as quickly as possible. They came to this conclusion after comparing images of the empty collector head with Oct. 22 images of the TAGSAM head after the sample collection event.
The images also show that any movement to the spacecraft and the TAGSAM instrument may lead to further sample loss. To preserve the remaining material, the mission team decided to forego the Sample Mass Measurement activity originally scheduled for Saturday, Oct. 24, and canceled a braking burn scheduled for Friday to minimize any acceleration to the spacecraft.
From here, the OSIRIS-Rex team will focus on stowing the sample in the Sample Return Capsule (SRC), where any loose material will be kept safe during the spacecraft’s journey back to Earth.
“We are working to keep up with our own success here, and my job is to safely return as large a sample of Bennu as possible,” said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona in Tucson, who leads the science team and the mission’s science observation planning and data processing. “The loss of mass is of concern to me, so I’m strongly encouraging the team to stow this precious sample as quickly as possible.”
The TAGSAM head performed the sampling event in optimal conditions. Newly available analyses show that the collector head was flush with Bennu’s surface when it made contact and when the nitrogen gas bottle was fired to stir surface material. It also penetrated several centimeters into the asteroid’s surface material. All data so far suggest that the collector head is holding much more than 2 ounces of regolith.
OSIRIS-REx remains in good health, and the mission team is finalizing a timeline for sample storage. An update will be provided once a decision is made on the sample storage timing and procedures.
NASA’s Goddard Space Flight Center in Greenbelt, Maryland, provides overall mission management, systems engineering and the safety and mission assurance for OSIRIS-REx. Lockheed Martin Space in Denver built the spacecraft and is providing flight operations. Goddard and KinetX Aerospace of Tempe, Arizona, are responsible for navigating the OSIRIS-REx spacecraft. OSIRIS-REx is the third mission in NASA’s New Frontiers Program, which is managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Science Mission Directorate in Washington.
Quelle: NASA