Mission: Hayabusa 2 Options

[Quetzalcoatl]

Bonjour

News of Hayabusa2’s return trip :

http://www.hayabusa2.jaxa.jp/en/topics/20200513_2nd/

[Roman Tkachenko]

HIT THE ASTEROID!
Hayabusa2 touchdown on asteroid Ryugu

[Tom Tamlyn]

So where's the swear jar these days?

[Marcin600]

Minerva-II2 orbiting around Ryugu - unpublished (?) pictures/videos from the monitoring of Minerva-II2 movement can be seen in the presentation (in Japanese) by Mr. Yuya Mitsuhashi, a member of the Hayabusa2 project, on June 20, at Hamagin Children's Space Science Museum (1st Hamagin Kids Science Talk Event) -

- posted on Youtube: from 1:33:25 to 1:38:50

These pictures may not be spectacular, but they are scientifically important (study of the gravitational field around Ryugu)

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[Marcin600]

An interesting topic has appeared on the JAXA’s Hayabusa2 website: "Ryugu's porous boulders covered rough surface, everywhere!" , presenting a new paper that has been published in the electronic version of Icarus: Shimaki et al., 2020 „Thermophysical properties of the surface of asteroid 162173 Ryugu: Infrared observations and thermal inertia mapping”

Two quotes:
„...As a result, it is found that the thermal inertia of the surface of Ryugu is ubiquitously small and porous boulders are distributed all over the surface of Ryugu. Additionally, the surface of Ryugu is as rough as the surface of Hawaii's a'a lava (degrees of roughness for Ryugu is several meter squares, whereas that for a'a lava is several tens centimeter squares, respectively)...”

„...The global surface roughness of Ryugu, covered by numerous boulders, was estimated to be 0.41 ± 0.08, corresponding to the RMS surface slope (average slope of a rough surface) of 47 ± 5°. The RMS surface slope of Ryugu is comparable to that of Hawaii's a'a lava. Note that the RMS slope of Ryugu is for several meter squares, but that of a'a lava for several tens centimeter squares, respectively. These similarities are only in their morphologies, so they do not represent similarities in the compositions and formation processes (Ryugu's boulder is expected to be carbonaceous chondrites rich in organics, but a'a lava is a basaltic igneous rock). However, these results suggest that large-scale roughness can be maintained on the surface of Ryugu because of the tiny gravity and no-weathering environment...”

[Marcin600]

A new topic has appeared on the Hayabusa2 website: "ONC reveals the dark and carbon-rich nature of Ryugu", discussing new article in the journal Astronomy and Astrophysics: Tatsumi et al. Global photometric properties of 162173 Ryugu


Some quotes:

„...We found that the geometric albedo is 4.0±0.5 % and standard reflectance is 1.87±0.14 % for Ryugu...
...This suggests that the carbon contents of Ryugu is very high >2 wt. %...

(...Geometric albedo: The ratio brightness of the object observed at phase angle 0˚... Standard reflectance (Reflectance factor at standard geometry): The ratio brightness of the object observed at phase angle 30˚...)

...the reflectance and carbon contents of thermally metamorphosed carbonaceous chondrites (...) which are considered to be similar to Ryugu composition...

...We still don’t know what kind of compounds the carbon is forming. However, so far organic compounds have been widely found in the carbonaceous chondrites. We therefore expect to see large amount of organic compounds from Ryugu’s returned samples...

...Our observational results [of the phase reddening effect] suggest that the presence of fine grains or structure on the Ryugu surface. Surprisingly, the reflectance and degree of phase reddening effect of Ryugu are very similar to those of Bennu... This suggests that the surface properties of the two objects may be very similar. So far, we knew of a few similarities between Ryugu and Bennu, for example density and shape, and now we found a further similarity in reflection properties. On the other hand, there is a difference in hydration degree; Bennu is more hydrated than Ryugu...”

[Marcin600]

From the Hayabusa2 website:

„We have also released a map [several maps] of the place names on the surface of asteroid Ryugu! Please see the gallery on the Hayabusa2 website: http://www.hayabusa2.jaxa.jp/galleries/fig/ "

©JAXA:

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[Marcin600]

From HAYABUSA2@JAXA twitter:

"A joint statement between JAXA and the Australian Space Agency (ASA) was announced today (7/14).
The Hayabusa2 re-entry capsule will return to Earth and land in South Australia on December 6, 2020 (Japan/Australia time).
This is in 145 days: R-145!"

[Marcin600]

A talk event took place on July 11 at “Hamagin Children's Space Science Museum”- Hayabusa2 project member Futo Terui, in charge of navigation guidance and control system, talked, among others, about pinpoint touchdown. JAXA posted it on YouTube (in Japanese)

There are some interesting videos, e.g. from dropping the target marker (2018/10/25 TD1-R3 TM) - I think they were not published before (?)


Cut out movie fragment (©JAXA):

Attached File(s)

 2020_Hayabusa2_h.mp4 ( 1.8MB ) Number of downloads: 394

 

[Paolo]

just published and in free access:

Global photometric properties of (162173) Ryugu

Context. The Hayabusa2 spacecraft launched by Japan Aerospace Exploration Agency has been conducting observations of the asteroid (162173) Ryugu since June 2018. The Telescopic Optical Navigation Camera (ONC-T) onboard Hayabusa2 has obtained thousands of images under a variety of illumination and viewing conditions.

Aims. Our objective is to examine and validate the camera calibration, derive a photometric correction for creating global albedo maps, and to interpret the photometric modeling results to characterize the surface of Ryugu.

Methods. We observed (162173) Ryugu with the Gemini-South telescope, and combined these measurements with other published ground-based observations of the asteroid. The ground-based observations were compared with the data obtained by ONC-T in order to validate the radiometric calibration mutually. We used a combination of the Hapke disk-integrated and disk-resolved model equations to simultaneously analyze the combined ground- and spacecraft-based data.

Results. The average spectrum of Ryugu was classified as Cb-type following the SMASSII taxonomy and C/F-type following the Tholen taxonomy based on spacecraft observations. We derived Hapke model parameters for all seven color filters, which allowed us to photometrically correct images to within an error of <10% for ~80% of the image pixels used in the modeling effort. Using this model, we derived a geometric albedo of 4.0 ± 0.5% (v band) for Ryugu. The average reflectance factor at the standard illumination condition was 1.87 ± 0.14% in the v band. Moreover we measured a phase reddening of (2.0 ± 0.7) × 10−3 μm−1 deg−1 for Ryugu, similar to that observed for the asteroid (101955) Bennu.

Conclusions. The global color map showed that the general trend was for darker regions to also be redder regions, however there were some distinct exceptions to this trend. For example, Otohime Saxum was bright and red while Kibidango crater was dark and blue. The darkness and flatness of Ryugu’s reflectance might be caused by a high abundance of organic materials.

[abalone]

The Hayabusa 2 spacecraft will release a sample return canister as it approaches Earth, then divert itself away from the planet and continue into space.
https://spaceflightnow.com/2020/07/16/aster...th-in-december/

[Paolo]

it appears that Hayabusa secondary mission will finally be a long-term one with arrival at its new target in the late 2020s or early 30s
https://twitter.com/haya2e_jaxa/status/1285864588622192640

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[Explorer1]

Looks like an interesting decision to make: a trajectory with a longer travel time to the rendezvous but another asteroid flyby in the meantime, or a shorter flight time but including a Venus flyby.
Either way, these rocks are absolutely tiny (Half the size of the ISS), definitely the smallest objects ever visited by a spacecraft (including the Didymos moon). Exciting!

[Holder of the Tw...]

Yes, half the size of the ISS but at least several hundred times the mass. And in both cases some of the most accessible off world mass we currently know of, more so than anything on the moon.

Aside from that, some speculation on the end of mission. Will Hayabusa 2 end its days by landing on its final asteroid? If it does, then a polar landing is mandated, because anywhere else and the spacecraft will simply be flung off by rotational force. Given the relative size of the spacecraft to whichever asteroid, it will become a rather significant new surface feature. Hayabusa Mons? Hayabusa Saxum?

[Explorer1]

I also wonder how long Hayabusa2 would need to "station-keep" on one side of the asteroid to measure the gravity tractor concept. We would need to know the mass first to do a calculation, plus knowing how much fuel is left by the time of the rendezouvs... there might be a good planetary defense method test opportunity here.