Earth Return & Sample Science Options

[Marcin600]

A final Bennu flyby is planned for April to check out the sampling site (not confirmed, but "if feasible")! 3.2 km closest approach, and also an opportunity to check the instruments are working well and not too affected by dust kicked up during the TAG.

https://www.asteroidmission.org/?latest-new...eroid-departure

It's a good news !!! I keep my fingers crossed for the OSIRIS-REx team - so that we can see this "battlefield" in April. It's now or never again !

[Marcin600]

"The International Astronomical Union (IAU) has approved more names for surface features on Bennu": https://twitter.com/OSIRISREx/status/1356300951942963200

https://www.asteroidmission.org/iau-features-3/


PS. But ... they're not officially listed yet here: https://planetarynames.wr.usgs.gov/SearchRe...ts?target=BENNU Why?

On the OSIRIS-REx website’s map I also can not see such (mentioned in the attached text) surface features, as: dorsa and fossae. Only the new names of the craters have appeared,
i.a. OSPREY is now Wuchowsen Crater; NIGHTINGALE is now Hokioi Crater etc.

[Marcin600]

A final flyby of Bennu (and Nightingale) on April 7 is approved !!!
https://www.asteroidmission.org/?latest-new...l-tour-of-bennu

„...The OSIRIS-REx mission team recently completed a detailed safety analysis of a trajectory to observe sample site Nightingale from a distance of approximately 2.4 miles (3.8 kilometers)...
...During this new mission phase, called the Post-TAG Observation (PTO) phase, the spacecraft will perform five separate navigation maneuvers in order to return to the asteroid and position itself for the flyby. OSIRIS-REx executed the first maneuver on Jan. 14 (...) the spacecraft is now slowly approaching the asteroid and will perform a second approach maneuver on Mar. 6 (...) OSIRIS-REx will then execute three subsequent maneuvers, which are required to place the spacecraft on a precise trajectory for the final flyby on Apr. 7 (...) OSIRIS-REx is scheduled to depart Bennu on May 10...”

[Marcin600]

„This image...was taken...on March 4, from a distance of about 186 miles (300 km)...during the mission’s Post-TAG Operations phase, as the spacecraft slowly approaches Bennu in preparation for a final observational flyby on April 7.” - https://www.asteroidmission.org/galleries/s...ennuagain/#main

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[Marcin600]

"...As of Mar. 12, the spacecraft was about 155 km from Bennu and approaching the asteroid at about 24.6 cm/s..." - https://www.asteroidmission.org/status-updates/

[alan]

Saw this on twitter:

Jason Major @JPMajor
Boulders of all sizes on the surface of the asteroid Bennu, imaged by @OSIRISREx two years ago on March 22, 2019. I inserted a Buzz Aldrin for comparative scale size.

[Marcin600]

"The OSIRIS-REx spacecraft... is currently about 30 km from the asteroid... Bennu – traveling approximately 6 cm/s..." - https://www.asteroidmission.org/?mission_update=mar-29-2020

[Marcin600]

https://www.asteroidmission.org/?latest-new...-asteroid-bennu

„...NASA’s OSIRIS-REx completed its last flyover of Bennu in around 6 am (EDT), 4am (MDT) April 7th and is now slowly drifting away from the asteroid; however, the mission team will have to wait a few more days to find out how the spacecraft changed the surface of Bennu when it grabbed a sample of the asteroid...”
„... It will take until at least April 13th for OSIRIS-REx to downlink all of the data and new pictures of Bennu’s surface recorded during the flyby. It shares the Deep Space Network Antennae with other missions like Mars Perseverance, and typically gets 4-6 hours of downlink time per day...”

[pbanholzer]

Marc - Thanks for the updates. Do you know what the pressurization of the nitrogen as released ? Oh, and fwiw I retired five years ago from 292.

[Marcin600]

I was unable to find information about the exact pressure of compressed nitrogen in 3 cylinders. The descriptions only use the terms compressed nitrogen or pressurized/high-pressure nitrogen bottles. Maybe someone has such data at hand ?

However, we must remember 3 things:
1. When we talk about gas pressure, we mean the pressure under Earth conditions (including the so-called standard temperature).
2. The pressure of the gas depends on its temperature. The colder the gas, the less pressure it has.
3. There is a vacuum on the surface of Bennu. Even gas under "normal" pressure released from the cylinder will behave as compressed gas there.

Here are some quotes found in articles on this topic and pictures of the actual 3 nitrogen cylinders on TAGSAM:

"TAGSAM is the product of Lockheed Martin. The complete TAGSAM design consists of (...) three pressurized bottles containing curation-grade nitrogen gas with a small amount of helium (to check leaks prior to launch)...
There are three independent gas bottles (which are independently released), to support up to three sampling attempts...
Gas handling is passive, operating in the simple blow-down mode...
Sample collection occurs when surface contact is sensed. At this point, a pyro valve opens to a bottle of high-purity nitrogen gas... When sample gas is released from a high-pressure bottle, the gas flows through a feedline to the head and is directed into the regolith via an annular aperture...
The majority of the gas release occurs in 5 sec ...
The gas mobilizes material underneath the head as the gas expands into the regolith. The flange seal and impedance of the soil bed cause the gas naturally to flow from the high-pressure environment underneath the head to the vacuum of space via the collection volume around the perimeter of the head. A screen around the perimeter of TAGSAM retains asteroid regolith, even as the gas escapes...

The propagation of the gas through the regolith likely occurs at hypervelocity speeds for much or all of its expansion. The initial peak speed of the gas while exiting TAGSAM is around 800 m/s. Because the porosity in Bennu's regolith is occupied by a vacuum rather than an atmosphere, the expansion of the gas through the interstitial spaces of the regolith will be a choked flow. In the case of choked flow, the expansion speed of the gas is its sound speed, which depends on gas temperature...

The TAGSAM gas reaches equilibrium with the environment as it expands unto the subsurface. Thus, the temperature of the gas is controlled by the ambient temperature...

The dynamics of the sample gas, and the response of regolith, will be different in Earth-atmospheric and gravity conditions versus those on Bennu...

In the gravity regime, the speed of the nitrogen gas through the regolith spans from the peak speed of release from TAGSAM, ~800 m/s, to the “steady state” expansion of the gas through the subsurface, around 325 m/s for 255 K.

Ground-based Earth testing has an ever-present gravitational acceleration of 9.8 m/s2, which is about 100000 larger than the gravitational environment at Bennu...
On the Earth’s surface, the weight of a cm-sized particle is a larger force than the aerodynamic lifting force of flowing gas unless the wind speeds are high (fortunately, most windy days on Earth do not loft cm-sized gravel into the air). In contrast, the weight of a 1-cm particle on Bennu is roughly 100000 less than on Earth because Bennu’s surface gravity is 10000 less than Earth’s surface gravity, yet the gas-driven forces remain the same...

Although there was thermal control on the gas delivery system, the hot case corresponds to an increased bottle pressure over the cold case, and as a result the hot case had higher bottle pressures compared with the cold case..."


A lot of details are e.g. here:
https://link.springer.com/content/pdf/10.10...-018-0521-6.pdf
https://www.sciencedirect.com/science/artic...20304826#bb0085
https://arxiv.org/ftp/arxiv/papers/1702/1702.06981.pdf

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[pbanholzer]

Thanks so much for all of this. More than I expected! I was curious about the force imparted to the sample - visually, it was obviously very strong and was designed for a different surface. I'll take some time to read the articles. I'm annoyed that I didn't use Tagsam as a keyword in my searches . :-)

[Explorer1]

Images released:
https://www.nasa.gov/feature/goddard/2021/n...-asteroid-bennu

Video here:
https://www.youtube.com/watch?v=J8ylW0SVplM

[Explorer1]

Press conference and new images to be released Monday, together with the Earth return burn:
https://www.nasa.gov/press-release/nasa-inv...eturn-to-earth/

[Marcin600]

Jun 04, 2021: "NASA’s OSIRIS-REx spacecraft is 328,000 miles, or 528,000 kilometers, away from the asteroid Bennu (...) The May 10 departure maneuver was calculated and executed so precisely, the mission team decided not to do a clean-up maneuver last week. The next possible maneuver adjustment could occur in 2022." - https://www.asteroidmission.org/?mission_update=jun-3-2021

[vjkane]

NASA has put out its call for proposals for extended missions (the regular senior reviews) https://www.lpi.usra.edu/NASA-academies-res...2PMSR-FINAL.pdf. For the OSIRIS-REx mission, it has specific guidance, "The OREx mission will be reviewed at this PMSR, ahead of its nominal schedule, in order to evaluate opportunities for spacecraft operations after the Sample Return Capsule has been released from the spacecraft. OREx should submit a proposal which describes an encounter with the asteroid Apophis in 2029-2031. The proposal should cover the time period FY23-FY31, including cruise, encounter, and closeout."

An abstract for the potential encounter is attached.

The other missions to be reviewed are InSight, LRO, Odyssey, MRO, MSL, MAVEN, and New Horizons.

Attached File(s)

 OSIRIS_REx_at_Apophis_2020.pdf ( 125.09K ) Number of downloads: 230