Mission: Hayabusa 2 Options

[pandaneko]

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?

P

[Explorer1]

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.

[pandaneko]

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.

P

[pandaneko]

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.

P

[Hungry4info]

15 May 2018. Star-tracker has detected Ryugu.

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

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).

[pandaneko]

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).

P

[pandaneko]

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.

P

[Phil Stooke]

Less than 24000 km to go! But who's counting? (hint: me!)

Another new world about to be revealed. This is going to be a very cool mission.

Phil

[pandaneko]

24 May (144km/h): 16/11/18/10/15/13/19/8/9/9/7/8

I want to continue , for some time to come, with this above to see if it is useful. This is the speed of Hayabusa 2
with chemical thrusters cumulative burn time (numbers are rounded). Neither Hayabusa 2 nor Haya2 web page
indicates significant changes in the flight in an easy to understand manner, so I decided to monitor what chemical
thrusters are doing.

It may be that only ion engines are used until Hayabusa 2 comes to a halt and in that case no significant changes
will have been made to above matrix of numbers (right now only one row). This matrix will continue to build up unil
it is 7 rows. If nothing has happned by that time a new matrix will appear wih its first row being the latest
input into Hayabusa 2 web page.

That way, we may be able to know when the landing gear is out.

P

[pandaneko]

24 May (144km/h): 16/11/18/10/15/13/19/8/9/9/7/8
25 May (144km/h): 16/11/18/10/15/13/19/8/9/9/7/8

No change, yet...

P

[nprev]

Is the landing gear supposed to deploy THIS early? Thought it was going to spend some time in orbit surveying the asteroid before attempting to touch down.

[Phil Stooke]

just an analogy? Does it even have landing gear? I think the drogue chute might be enough.

Phil

[nprev]

The landing gear would be for touchdown on the asteroid, I think. Return capsule should indeed be just the aeroshell & chute, no legs.

[pandaneko]

Is the landing gear supposed to deploy THIS early?

I am unsure as it is now such a short distance to the target, but point taken and I will do it in my backyard!

P

[pandaneko]

just an analogy? Does it even have landing gear? I think the drogue chute might be enough.

Phil

I have been using "landing gear being out" to mean a significant reduction in speed. My matrix was
a means to feel the onset of slowing down, but overnight from yesterday to this morning
Hayabusa2's speed went down from 144km/h to 108km/h, and it is pretty clear, I think, that
the breaking power of ion engines alone is good enough to make Hayabusa2 to come to a halt
without relying on chemical thrusters.

I am excited to see this asteroid!!! 加油！！！

P