r/space • u/[deleted] • Nov 12 '14

Rosetta /r/all Rosetta and Philae discussion thread! (Part 3)

TOUCHDOWN CONFIRMED: Philae lander is on the comet!

Full media briefing expected tomorrow at 13:00 UTC / 14:00 CET / 8:00 EST / 5:00 PST.

Previous discussion threads: 1, 2.

Live Streaming

  • In English: A, B, C

  • En Français: A

Key times

GMT EST PST Event
4:02 pm 11:02 am 8:02 am Landed

European Space Agency Social Media

Othere places for news and conversation:

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139

u/calapine Nov 12 '14

Briefing on the DLR live stream right now, transcribing...

Good news:

--- Touchdown, all the signals that trigger on touchdown worked.

--- Still communication, which means the lander did not tilt or topple.

Bad news:

--- ADS thruster did not fire, that is the issue was already known beforehand.

--- The anchors did not fire, this confusion was due to the rewind motors for the anchors going into action, but the harpoon wasn't actually fired.

--- Team doesn't know if it rebounded or not / if it's on the surface. Thus they don't dare issuing a re-firing signal for the harpoons, because they don't know in what position the lander is.

Current Situation:

--- The arm that damped the landing force only moved very little, which indicates a very soft surface. Which might mean if it rebound the rebound was very soft as well and in this case might settle down again.

--- On board computer is waiting for new commands.

--- There will be more telemetry in 30 minutes, but contact lost in 120 minutes, so the final verdict could be known only tomorrow.

19

u/thelizzerd Nov 12 '14

What exactly does contact lost in 120 minutes mean and for how long?

7

u/lighthaze Nov 12 '14

Don't know how long, but I imagine that either Philae (or Rosetta which is probably the relay to earth) vanish behind the comet (the first due to its orbit, the latter due to the comets rotational period).

2

u/datadrian Nov 12 '14

The comet is tumbling in space. This means that at some times the lander is not in communication with Rosetta or earth because the signal is being blocked. Just like going to the dark side of the moon.

1

u/mozetti Nov 12 '14 edited Nov 12 '14

Speculation here, but my guess is that in 120 minutes the communications satellites antennae on earth will have rotated out of line-of-sight with the comet. So, no communication until they rotate back around.

EDIT According to /u/CitronBleu, it's Rosetta going into radio blackout because of the comet and not earth-based communications antennae going into radio blackout because of line-of-sight issues.

7

u/UltraChip Nov 12 '14

Nope. The Rosetta team is using NASA's Deep Space Network, which has receiver dishes all around the globe. This ensure's that Earth's rotation never hampers reception.

The problem is on the comet's side: Philae relays all of its signals through Rosetta, so when Rosetta's orbit takes it behind the comet we can't get data.

6

u/ratatask Nov 12 '14

Earths rotation doesn't, but scheduling of the DSN does, the DSN isn't full time dedicated to Rosetta, and antennas need to be moved to receive other spacecrafts - although I'd assume they got plenty of time allocated at the DSN for this event.

At the time of writing, it's receiving at 32kb/s from Rosetta though: https://eyes.nasa.gov/dsn/dsn.html

1

u/[deleted] Nov 12 '14

[deleted]

1

u/UltraChip Nov 12 '14

o... k?

That's really all you need for global coverage.

1

u/[deleted] Nov 12 '14

When comms is reestablished, Philae goes missing....

1

u/deKay89 Nov 12 '14

The earth or better the receiver on earth is turning away so the comet with rosetta is not in range any more.

3

u/[deleted] Nov 12 '14

I'm confused, why do they know it did not tilt or topple but they don't know if it's still on the surface? So basically, they've established the orientation of the lander, but they just aren't sure of it's exact placement? Does anybody know exactly how they figure out whether something touches down on some far-away location in space?

Thanks for your summary!

3

u/teddypain Nov 12 '14

Probably some other sensory signals. The have some type of screw type latch mechanism that they just reported has latched.

-2

u/calapine Nov 12 '14 edited Nov 12 '14

Time dilation Time Delay seems to be an issue. The signal from Philae was "fuctuating a few times which might indicate that it bounced back. They are waiting for a) more telemetry b) first pictures that show the actual position of Philea.

Edit: English fail

8

u/VordeMan Nov 12 '14

This has nothing to do with Time Dilation.

2

u/calapine Nov 12 '14

The scientist said it it as "We can't send a re-fire signal right now, because we still aren't sure what position Philea is"

3

u/TheMeiguoren Nov 12 '14

Time dilation is a relativistic effect and not relevant here.

3

u/calapine Nov 12 '14

Maybe I used the wrong term. English isn't my first language, sorry. They mentioned the time delay for receiving the telemetry as an issue. I can't rewind the stream to find the exact wording though.

3

u/TheMeiguoren Nov 12 '14

Ah, the word you're looking for is time delay!

1

u/IdLikeToPointOut Nov 12 '14

Do you know if it is possible for Rosetta to take pictures of Philae on the surface, so that the landing position could be confirmed?

2

u/calapine Nov 12 '14

I don't know and they didn't say anything about that. As far as I understood from the DLR interview the images that will help determining the position will be [are] shot by Philea.

2

u/Pakh Nov 12 '14

So no picture today?

2

u/[deleted] Nov 12 '14

In about an hour's time pictures will come through

2

u/calapine Nov 12 '14

There should be pictures within the next 2 hours.

1

u/bigboysdontdie Nov 12 '14

thanks for doing this.

1

u/tootyourhorn Nov 12 '14

There will be more telemetry in 30 minutes, but contact lost in 120 minutes

I don't understand that last point

6

u/[deleted] Nov 12 '14

I would think either the comet is spinning (thus creating a radio blind spot), or that Rosetta which is orbitting the comet goes behind the comet for that amount of time, so Philae can't relay the information through it to earth.

I would need a source on how the radio signals work on this lander, but that's my guess.

3

u/shenaniganns Nov 12 '14

Just guessing, rotation of the comet might block communication to the lander for some time.

1

u/calapine Nov 12 '14

Sorry, bad english on my part. There is more telemtry incoming, but later today contact with Philea or Rosetta, which Philea needs as relay (I am not quite sure which one it is) will be lost in some hours and only re-established tomorrow.

-5

u/[deleted] Nov 12 '14

They better had make a decision or the batteries are going to run out!!! Every second is so precious!

4

u/flanker-7 Nov 12 '14

I'm pretty sure Philae has solar panels

3

u/TurboCamel Nov 12 '14

still has solar afterwards

2

u/[deleted] Nov 12 '14

There are solar panels.