IonStorm

It's almost time to touch Bennu. Follow along on NASA TV starting at 5pm EDT/21:00 UTC on Tuesday 20 October 2020 and a live stream of the STK simulation at https://www.asteroidmission.org and follow @OSIRISREx Until them watch in 3D. https://youtu.be/KGdooPr8XfI See what can go wrong (no F9 allowed)! https://youtu.be/0NlZlJAVnDA Or maybe learn a bit about the sample science: https://youtu.be/HCrwF4oBCvk

Announcement This Thursday, Sept. 24, OSIRIS-REx will hold a briefing to update members of the media on our sample collection efforts and to spread our excitement about TAG to the public. The briefing will be broadcast over NASA.gov. Details below: Date: Sept. 24 Time: 1900 UTC/3:00 pm EDT/12:00 pm PDT Website: Teleconference audio and visuals will stream live at www.nasa.gov/live Participating in the mission update are: • Thomas Zurbuchen, associate administrator of NASA’s Science Mission Directorate • Lori Glaze, director of NASA's Planetary Science Division • Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, Tucson • Mike Moreau, OSIRIS-REx deputy project manager at NASA’s Goddard Space Flight Center • Sandra Freund, OSIRIS-REx mission operations manager at Lockheed Martin Space And between now and TAG – follow the mission on Twitter, Facebook, and Instagram and our websites www.nasa.gov/osiris-rex and www.asteroidmission.org – to get in on the excitement.

Fantastic! I hadn't realized it was out of beta yet. We're still working on getting our color mosaic MapCam data released as a layer (don't get too excited, the colors are really subtle).

No F9 required. A perfect rehearsal. https://www.asteroidmission.org/?latest-news=a-successful-second-rehearsal-puts-nasas-osiris-rex-on-a-path-to-sample-collection

The name OSIRIS-REx? We picked OSIRIS in 2004 to describe the mission goals: Origins Spectral Interpretation Resource Investigation Security We proposed OSIRIS twice as a Discovery class mission. After OSIRIS was not selected after a Phase A study (the Grail mission was selected instead), heart-broken, we needed to re-propose in the New Frontiers program. New Frontiers requires a bigger scientific impact than Discovery, so initially as a joke in 2008 we added Rex after OSIRIS since it would be bigger, kingly, T. rex like. Mixing Egyptian with Latin was odd, but oh well. We then bacronymed Rex into REx for Regolith Explorer. It is fortunate that OSIRIS wasn't selected. Bennu has been much more challenging than predicted with the best science at the time and we have needed every bit of the extra capabilities provided by a New Frontiers class spacecraft. See also, https://dslauretta.com/2015/01/22/osiris-rex-whats-in-a-name/

Tomorrow is a very important milestone for the OSIRIS-REx mission - the final rehearsal before sample collection! We invite you all to join us for a live play-by-play on Twitter August 11 at 2:30 EDT on Twitter@osirisrex The OSIRIS-REx team (following social distancing and wearing masks) will conduct its Matchpoint Maneuver Rehearsal over the Nightingale Site on asteroid Bennu. There will be a 16 minute one-way communication delay between the spacecraft and Earth. So the event commands will be uploaded to the spacecraft and the maneuver will be conducted autonomously. The low gain antenna will transmit data to Earth with images and science data downlinked when the rehearsal is completed. For more details on the Matchpoint Maneuver and a summary poster.

Here is the full high resolution mosaic of the prime sampling site https://www.asteroidmission.org/nightingale-recon-c-mosaic-reduced-size/

You can also look at all the images released to the public in batches 6 months after collection here https://sbib.psi.edu/data/PDS-Bennu/index.html? This doesn't have the mosaics, which are data processed and doesn't yet have Recon C images. I am able to open the giant mosaics with Preview on macOS, btw.

The surface is super dark with a few comparatively bright spots. The dark spots are like coal and the bright spots are like the Moon. You can compare that to the 380MB global mosaic. It has about 1/10 the resolution but the whole asteroid https://www.asteroidmission.org/bennu_global_mosaic/

Successful low recon pass over Osprey (20k x 12k image) https://www.asteroidmission.org/osprey-recon-c-mosaic/ Recall that the medium pass images over Osprey were out of focus due to the OLA failure, so this a big improvement of the imaging of the backup site.

COVID-19 has impacts in space too. TAG delayed from August to October 2020 https://www.asteroidmission.org/?latest-news=nasas-osiris-rex-ready-for-touchdown-on-asteroid-bennu

So, I did a NASA podcast on OSIRIS-REx: https://www.nasa.gov/mediacast/gravity-assist-a-special-delivery-of-life-s-building-blocks-with-jason-dworkin

Flawless execution, even though the team was isolated. Special thanks to the Madrid DSN station who received the data.

The Checkpoint Rehearsal is tomorrow!

We have speculated, "The retention of large craters on Bennu’s equatorial ridge requires that the surface age predates the expected approximately 10-million-year duration as a NEA. There is no clear geologic indication of the process that formed the ridge, and given its relation to the large craters it could be a feature preserved from the formation of Bennu, which would make it the oldest feature on its surface. Bennu’s surface therefore also recorded processes from its time in the main belt; the formation timescales of the largest craters suggest that Bennu recorded hundreds of millions of years of history during this period." (Walsh et al., 2019) https://science.gsfc.nasa.gov/sed/content/uploadFiles/publication_files/Walsh2019.pdf

Here is a Bennu global mosaic at 5cm/px. This is the best global resolution that will be obtained. https://www.asteroidmission.org/bennu_global_mosaic/

So it was something deeper after all, but restricted to the low power laser not the whole instrument. The high power laser will be used instead. It is sufficient resolution for focusing and does not require a big software change:

Here is a 20 cm resolution animation of the shape model and image overlay of Bennu for your amusement. Again this animation is from 100% real data. https://svs.gsfc.nasa.gov/vis/a000000/a004700/a004795/Bennu_spin_full_20cm_1080p30.mp4 This was used in this video:

This can happen either due to random single event errors (i.e. cosmic ray hits) or something deeper. OLA has been asked to do additional work beyond its requirements due to the extra imaging required for the rocky surface. It is expected that some fraction of the images will be out of focus by an unknown amount, we will see when it gets downlinked. There is a Guidance and Navigation LIDAR which was to have been used for sampling--if the asteroid wasn't so rocky. This could be reprogrammed to help PolyCam focus--this will take time. Just reflying the pass to retake the bad images would take less time.

If you want to browse images from the ~six months of Bennu encounter (18 Oct 2018 - 12 April 2019), the complete image data set are public at the Planetary Data System in a simple GUI https://sbib.psi.edu/data/PDS-Bennu/ (unlike the usual PDS distribution method https://pds-smallbodies.astro.umd.edu/data_sb/target_asteroids.shtml#101955_Bennu)

The sample return canister (SRC) is sealed, but not airtight. There is a filter (Figure 1 and 2) allows the pressure inside to equalize with the outside during reentry without introducing water or heatshield ablation products. Upon collection the SRC is kept under N2 purge to prevent ingest of moisture and contaminants. Otherwise, the canister would need to be heavy enough to hold vacuum, which is more expensive than OSIRIS-REx can afford. Also, based on the nitrogen agitation to collect the sample, the warm surface temperature of Bennu, and reentry heating we don't expect a lot of loosely bound gases so it would not have been a good use of resources to build an airtight and thus and heavier return capsule. Instead we will be observing the gases that are evolved upon heating in the laboratory. Fig 1. Note the location of the filter inside the SRC in panel b Fig 2. Diagram of the filter Filter performance and other fussy details can be found at https://rdcu.be/bYXUe

It was a complex series of analyses and models with more than just the topographic models. We also used rock counting to the cm-scale, color variation, local tilts, and spectra. Osprey has slightly better backaway vectors but a lower density of fine material. So the probability of a successful contact times the probability of a successful collection for the two sites was about the same. After vigorous debate we selected Nightingale as prime and Osprey as backup and rejected the other two. We received concurrence from headquarters that our rationale is sound. Yes, we had modeled our pre-launch data based on Itokawa and expected vast smooth regions like the Muses-C regio and assumed worst case would be like the rough areas of Itokawa. Surprise!

Now check out the videos

It is a great site on a challenging asteroid. Next are some low passes to get even better images, then some rehearsals in the spring for sampling in August!

Earth rocks also can show linear cracks, but often with very different types or rocks than Bennu http://maps.unomaha.edu/maher/STEP07/supportinfo/cracks.html There are phyllosilicates (clays) on the surface, they could exhibit a preferred fracture orientation. It may be due to thermal fracturing, and perhaps related to the particle ejection events. So much science to do.