Starship Asterisk*

by **Jim Leff** » Sat May 24, 2014 4:18 pm

Chris Peterson wrote:
Jim Leff wrote:The orbiter has the mass of a pickup truck. The comet has the mass of a small asteroid - much less mass than Everest.

Or by "massive" do you mean "containing any mass at all"?
Yes.

By my quick calculation, the orbital speed works out to around 3 cm/s for a 200 km radius orbit.

Just doesn't seem intuitive to me. But nobody ever said physics had to be intuitive!

by **Chris Peterson** » Sat May 24, 2014 4:10 pm

Jim Leff wrote:The orbiter has the mass of a pickup truck. The comet has the mass of a small asteroid - much less mass than Everest.

Or by "massive" do you mean "containing any mass at all"?

Yes.

By my quick calculation, the orbital speed works out to around 3 cm/s for a 200 km radius orbit.

by **Jim Leff** » Sat May 24, 2014 3:31 pm

Chris Peterson wrote:Any two massive bodies will orbit each other given the proper velocity.

The orbiter has the mass of a pickup truck. The comet has the mass of a small asteroid - much less mass than Everest.

Or by "massive" do you mean "containing any mass at all"?

by **Chris Peterson** » Sat May 24, 2014 2:41 pm

Jim Leff wrote:The landing part just sounds difficult. It's the orbiting part I can't understand.

Why? Any two massive bodies will orbit each other given the proper velocity.

by **Jim Leff** » Fri May 23, 2014 11:52 pm

geckzilla wrote:Landing on something with such low surface gravity has its own challenges.

The landing part just sounds difficult. It's the orbiting part I can't understand.

by **RJN** » Fri May 23, 2014 6:34 pm

Gruyere wrote:Mmmmmmmmm ,,, gob-ular

"Globular." Fixed it. Sorry. - RJN

by **ta152h0** » Fri May 23, 2014 5:12 pm

as far as landing on an object of low gravity ? Remember EROS ? I just hope they remember the units they use to measure with

by **Chris Peterson** » Fri May 23, 2014 4:27 pm

MarkBour wrote:I noticed that today (+/- 1) is listed as the "rendezvous" date in some of the materials describing this mission.

That's confusing, isn't it? I think that what they are calling the "rendezvous" would be better described as the beginning of the rendezvous phase. The 21 May deceleration burn created the largest delta-V of any planned maneuvers. It began the process of putting the spacecraft in orbit.

Today's APOD ends with an image on May 4, about 19 days ago. You can clearly see the comet waking up and getting close. But if the Rosetta craft has now truly "reached" the comet, how long does it take for images to get here and to be processed for the awaiting public?

It hasn't reached the comet. Currently, the spacecraft is 27 light minutes from Earth (and 3 light seconds from the comet). ESA decides how quickly data is released, but it's generally almost immediately.

by **MarkBour** » Fri May 23, 2014 4:02 pm

Very nice sequence of images. It's surely a very exciting time for those who planned and executed this mission and have waited so long. I noticed that today (+/- 1) is listed as the "rendezvous" date in some of the materials describing this mission. Today's APOD ends with an image on May 4, about 19 days ago. You can clearly see the comet waking up and getting close. But if the Rosetta craft has now truly "reached" the comet, how long does it take for images to get here and to be processed for the awaiting public? I gather this will be a really wonderful ride. There's no substitute for being there!

by **Chris Peterson** » Fri May 23, 2014 3:56 pm

dickfrom1929 wrote:M104 is the Sombrero galaxy in Corvus. I don't see comet 67P close to M107 in Starry Night Pro.

We're seeing it by M107, not M104. That said, however, you can't evaluate a picture like this using a planetarium program unless you change your viewpoint from Earth to Rosetta. The comet is currently in Sagittarius as seen from the Earth, but in Ophiuchus as seen from Rosetta.

by **dickfrom1929** » Fri May 23, 2014 3:07 pm

M104 is the Sombrero galaxy in Corvus. I don't see comet 67P close to M107 in Starry Night Pro.

by **RJN** » Fri May 23, 2014 2:52 pm

starsurfer wrote:If the globular cluster is M107, then the background starfield belongs to Ophiuchus.

Yes, thank you. The APOD has now been updated with this more accurate information. We apologize for the oversights.

by **epszteinbenoit** » Fri May 23, 2014 2:34 pm

Very helpful, Geck, it's highly appreciated!

by **geckzilla** » Fri May 23, 2014 2:04 pm

Omaha science wrote:What is the star that winks on and off just to the right of the globular cluster in comet photo position 6 (by my count)?

Curious

All I see is a cosmic ray. It's one of the brighter ones.

by **Omaha science** » Fri May 23, 2014 1:15 pm

What is the star that winks on and off just to the right of the globular cluster in comet photo position 6 (by my count)?

Curious

by **BDanielMayfield** » Fri May 23, 2014 12:17 pm

Thanks Geck. And here's a wish for clear skies for everyone in North America southeast of Alaska for tonight's possible meteor storm!

by **geckzilla** » Fri May 23, 2014 11:57 am

BDanielMayfield wrote:As someone who often processes these images taken from cameras in space these cosmic ray flashes must cause you grief too (not nearly as bad as cancer, of course) as you painstakingly remove them. How difficult is that process Geck?

Depends on how many exposures there are. If there are a lot of exposures then it becomes largely automated. Fewer exposures results in uncertainty and a lot more manual removal. In cases where stars do not overlap between color channels such as when infrared light is used and many stars are invisible in shorter wavelengths, it is very difficult for me to make the distinction between a stellar point source and a cosmic ray which struck the sensor straight on. Hubble processing problems.

by **owlice** » Fri May 23, 2014 11:55 am

I've let the editors know re: Sagittarius and gobular star cluster M104.

by **starsurfer** » Fri May 23, 2014 11:45 am

If the globular cluster is M107, then the background starfield belongs to Ophiuchus.

by **BDanielMayfield** » Fri May 23, 2014 11:43 am

geckzilla wrote:
DougF wrote:Hi
I am curios what are all the other flashing lights in the photos
Doug
Cosmic rays. These are high energy particles which strike the camera sensor but they are cleared off next time an image is taken so they only appear for one frame at a time. These are also what will give astronauts cancer if they are not careful. Sometimes they are so energetic that they can damage a camera sensor, creating a permanent bad pixel.

As someone who often processes these images taken by cameras in space these cosmic ray flashes must cause you grief too (not nearly as bad as cancer, of course) as you painstakingly remove them. How difficult is that process Geck?

by **Gruyere** » Fri May 23, 2014 11:15 am

Mmmmmmmmm ,,, gob-ular

by **geckzilla** » Fri May 23, 2014 11:10 am

DougF wrote:Hi
I am curios what are all the other flashing lights in the photos
Doug

Cosmic rays. These are high energy particles which strike the camera sensor but they are cleared off next time an image is taken so they only appear for one frame at a time. These are also what will give astronauts cancer if they are not careful. Sometimes they are so energetic that they can damage a camera sensor, creating a permanent bad pixel.

by **Guest** » Fri May 23, 2014 9:18 am

melikamp wrote:...

P.S. finding astronomers' names for captcha is a REAL pain because I don't know some of the cheese names.

If it doesn't sound familiar, it's cheese. Tip: Use internet search to beef up your cheese and/or astronomers knowledge.

by **Boomer12k** » Fri May 23, 2014 9:15 am

Very cool....

And M104 is the Sombrero Galaxy...no doubt a Typo....

:---[===] *

by **Camiel Plevier** » Fri May 23, 2014 9:14 am

DougF wrote:Hi
I am curios what are all the other flashing lights in the photos
Doug

I was wondering the same thing. Could these be objects from the asteroid belt? It doesn't seem random noise to me.

Starship Asterisk*

APOD: Rosetta's Target Comet (2014 May 23)

Post a reply

Expand view Topic review: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)

Re: APOD: Rosetta's Target Comet (2014 May 23)