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Mission: Hayabusa 2
pandaneko
post May 14 2018, 12:14 AM
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QUOTE (charborob @ Apr 30 2018, 07:39 PM) *
It means the time it takes for electromagnetic waves to make the round trip from Earth to Hayabusa 2 and back.


Thank you Charborob. I thought that it might be somehow related to the flight time. It is some time sice I last looked at the relative
velocity. A few weeks ago it was 100m/s and now it is now down to 60m/s. That must mean that the ion engines are pointing to Ryugu. It makes
me uneasy because by the look of the diagram both telephoto (once used to catch a glimpse of the asteroid, about 5,6 weeks ago?) and
the wide angle cameras are pointing perpendicular to the flight direction.

Haya2 web page shows that it is now the wide angle camera in use, but it is not looking forward, yet, I think. Display window is totally
dark. I was hoping that Haya 2's display window will show us continous image of approaching Ryugu, but it seems very unliklely,
unless they use chemical thrusters on and off for us. How soon will we be seeing anything at all?

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Explorer1
post May 14 2018, 01:19 AM
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They already confirmed where Ryugu was back in February, they would have to stop firing the engines to turn the craft and take pictures. They will wait to be close enough to resolve it, presumably.
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pandaneko
post May 14 2018, 08:04 AM
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I have had a look at a radar image of the target asteroid for OSIRIS-REX. The image looked a bit wobbly, but it looked just like those
comments made about it, its shape in particular. And, presumably, by triangulation and experience with mereorites they can
estimate its mass.

I have seen comments that not much is known about Ryugu. How then did they estimate the escape velocity for MASCOT? My guess is
that the design velocity is far below the thinkable upper limit, so that MASCOT is not lost into space after its first hop?

My general cuoriosity is simply, how do they know anything at all about these asteroids from such a distant place like earth.

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pandaneko
post May 16 2018, 08:48 AM
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There is a consolation, after all, except that we do not know when it will be.

Haya2's pop-up for the display window translates as follows:

"Asteroid position and size. In the final stage of approach to Ryugu Hayabusa 2 will be showing approaching Ryugu
in the display window."

Very irritating. They could tell us roughly when it will be. Very bad PR activity, I think. Anyway, the relative velocity is now
down to 50m/s.

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Hungry4info
post May 16 2018, 10:43 AM
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15 May 2018. Star-tracker has detected Ryugu.

http://www.hayabusa2.jaxa.jp/topics/20180515_e2/

QUOTE
Hayabusa2 is currently operating its ion engines as the spacecraft approaches asteroid Ryugu. But on May 11, the ion engines were temporarily stopped so that the onboard Star Tracker (see note 1) could take a photograph of Ryugu. This observation of the direction of Ryugu from the spacecraft will be used for optical navigation (see note 2).


--------------------
-- Hungry4info (Sirius_Alpha)
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pandaneko
post May 18 2018, 12:43 AM
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There is a short article about Hayabusa 2 on today's local newspaper here. JAXA told the municipality of Sagamihara where
ISAS (part of JAXA) is located. Students in ISAS control room are operating Hayabusa 2. It confirms that the arrival of
Hayabusa 2 (apparently to the altitude of 20km) is 21 June (as opposed to a longer window starting from 21 June).

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pandaneko
post May 20 2018, 07:18 AM
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Below really is for myself.

As of 20 May the relative velocity is 180km/h, already slower than shinkansen trains. The distance to be closed is
38,000km, about two round trips bet. Tokyo and London. If this speed is maintained Hayabusa will reach Ryugu in
8.8 days, i.e. before the end of this month.

How soon it is to slow down further remains to be seen.

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