APOD: Rollback from GRAIL's Rocket (2011 Sep 10)

[APOD Robot]

Rollback from GRAIL's Rocket

Explanation: This dramatic time-lapse photo traces a 20 minute long, late evening rollback of the lighted Mobile Service Tower at Cape Canaveral Air Force Station Launch Complex 17. Twin spacecraft are snug inside the 13 story tall Delta 2 rocket poised for launch. The duo will journey to the Moon on NASA's Gravity Recovery and Interior Laboratory mission, GRAIL, using precision formation flying to map the Moon's gravity field. The scene was captured prior to the first launch attempt, canceled due to upper level winds, on September 8. Further launch opportunities for GRAIL begin this morning, September 10. The GRAIL launch is the last one planned from Complex 17 on Cape Canaveral's oldest still active pad, in use since 1957.

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[bystander]

http://asterisk.apod.com/viewtopic.php?f=8&t=20462

[bactame]

Boy that is a jim dandy rocket...need Frank Sinatra to fly me to the moon.

[orin stepanek]

Now we'll know what makes the moon tick!

[NoelC]

Great photography. Really eye-catching.

Will this mission be able to lay to rest whether there are any molten parts in the moon's interior still?

-Noel

[cj2255]

I see a person standing near the white van. Did they nor move for 20 minutes? I guess that's possible, but strange.

[BPCooper]

I think you are seeing a fire hydrant

Thanks!

[saturn2]

GRAIL mission is very important.
A map the Moon´s gravity field, is interesting for the space investigation.
Complex 17 of Cape Canaveral, in use since 1957, has a good record of work.
Congratulations!

[Jonathan SCE]

The EXIF data says that it the photo has a 179 second exposure time, so I do not know where they got 20 minutes.

[Case]

The EXIF data says that it the photo has a 179 second exposure time, so I do not know where they got 20 minutes.

Stacking 7 consecutive photos of 02m59s would get 20m53s total.

[Chris Peterson]

The EXIF data says that it the photo has a 179 second exposure time, so I do not know where they got 20 minutes.

Stacking 7 consecutive photos of 02m59s would get 20m53s total.

And note that you can't practically take a 20-minute exposure with a DSLR, since the uncooled sensor will largely fill with dark current in that time. 5 minutes is about the maximum exposure for a single frame without seriously compromising dynamic range, although you can still get good results in some cases out to around 10 minutes. For a shot like this, 3-minute subs make good sense.

[BPCooper]

Yea, it is a multiple exposure as Chris notes, to play it safe (I did test shots before it began, and my concern was more about the xenon lights they had already turned on. I stacked three ND filters on the lens for this shot). It's was actually three shots. The exif only records the length of one of them, probably the first or last, and they were a little different. It was probably actually less than 20 minutes looking it over again. I started the exposure after the tower was back enough that none of the lines of light would be in front of the rocket and then went until it reached the parked position. The whole roll was probably 20 minutes of moving time.

[DavidLeodis]

In information about the GRAIL mission brought up through a link it states "The two GRAIL spacecraft will be launched together and then will fly similar but separate trajectories to the Moon after separation from the launch vehicle, taking about 3 to 4 months to get there. They will spend about 2 months reshaping and merging their orbits until one spacecraft is following the other in the same low-altitude, near-circular, near-polar orbit, and they begin formation-flying". Elsewhere in the GRAIL website it states "GRAIL-A is scheduled to reach the Moon on New Year's Eve 2011, while GRAIL-B will arrive New Year's Day 2012".

I appreciate that getting the two craft precisely where they should be will take time, but about 3½ months does seem a lot.

[bystander]

I appreciate that getting the two craft precisely where they should be will take time, but about 3½ months does seem a lot.

http://asterisk.apod.com/viewtopic.php? ... 62#p156241

[DavidLeodis]

I appreciate that getting the two craft precisely where they should be will take time, but about 3½ months does seem a lot.

http://asterisk.apod.com/viewtopic.php? ... 62#p156241

Thanks for providing the link bystander, which is appreciated.

[BPCooper]

It's actually not "about three or four months." Their arrival was specifically December 31 and January 1.

[agulesin]

It's actually not "about three or four months." Their arrival was specifically December 31 and January 1.

I think he (David) means between launch and arriving at the moon. Well in these days of frugality NASA has to use slower rockets I suppose...