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ISON in STEREO!
The CIOC is excited bring you the very first images of comet ISON entering the NASA STEREO-A spacecraft SECCHI HI-2 field of view. [Click to animate!]I'll say this upfront: this is unquestionably not the most exciting or well-crafted animated gif you're ever going to see. But it's late, I'm tired, and there's only so much lipstick I can put on these images... That said, I urge you to click the image opposite to see the tiny speck in motion that is Comet C/2012 S1 (ISON) in the SECCHI HI-2 camera on NASA's STEREO-A spacecraft!
This is actually rather exciting! Not only does STEREO-A now enter the books as being the seventh spacecraft to have observed comet ISON, this is also something of a milestone in terms of spacecraft observations of ISON. From this day forth, comet ISON will remain in the field of view of the NASA STEREO-A (and in a few weeks STEREO-B) satellites until January 2014!
This is the first time these images have been seen, so we have a CIOC Exclusive here! That's the advantage of me being on the CIOC: you all get front-row seats for the STEREO and SOHO data! The data are from October 10th, and a little from the 11th, and I was able to get them because our data/operations gurus managed to snag the data much earlier than we typically do as part of our nominal processing pipeline. Expect to see increasing amounts of content like this from me over the coming weeks now...
Anyway, I don't want to make this too lengthy of a post (I genuinely am exhausted!) but very briefly, here's what you're seeing in that animation. Obviously comet ISON appears very small right now, as it is a long distance from the spacecraft, and the pixels in that image are very big. By that, I mean that each pixel of the image actually contains a fairly significant chunk of sky. By my very rough estimates based on previous experience with comets in that camera, I'd say ISON is somewhere around mag 10 -- which is more-or-less what ground observers are beginning to see, too. Also visible in the image are lots of bright blobs -- those are stars. The reason why they look so big and fuzzy is beyond the scope of my writing powers tonight. I'll cover it in detail another day. Finally, that funny wedge-shaped thing is something we placed in the instrument field of view for early during the STEREO mission (back in 2007-ish) when the Earth was in the field of view and would have blinded the camera if not for that little wedge.
It might help you to look at a full-resolution HI-2 image to get a feel for just how much I had to crop and zoom in there, so check out these much nicer processed HI-2 images when comet Lovejoy was still in the field of view (note: Lovejoy was much closer to the spacecraft and much brighter at that time -- don't try and compare ISON to it... yet...). I didn't apply the blue color scheme to the images in that animation, either. It's my intention to make a much longer/nicer movie when we have a few more days of data.
As you can see by its motion, ISON is heading into the field of view right now. I'd recommend you take a look at our September 23 Image of the Week to see the path the comet is going to follow. This animation more-or-less encompasses the very left-most red dot on the image we featured. So yeah, it's got a long way to go! But the good news is, it will get much brighter over the coming weeks, and by the time it leaves that field of view in late November we should be seeing some really nice tail dynamics as the solar wind interacts with the comet. So there's lots to look forward to!
OK, final thing -- and I'm definitely spoiling you now... The NASA STEREO data is completely public data - with absolutely no propriety period imposed upon it by NASA - but it usually takes a couple of days to propagate to online databases and such. But since this is a special occasion, and the STEREO data really is kind of fun to play with, I'm going to share my source images with you right now! (I/We will NOT make a habit of this - consider it a special occasion - as the CIOC is not a data host!) Here is a direct link to a 35MB zip file that contains twelve raw "FITS" data files. Right-click that link, save and unzip the file, and have fun! Note that you will need software that can handle a FITS data file, and ideally some astronomical processing software to help you. If you have absolutely no idea where to begin, this perhaps isn't the project for you, as it does help to have some background in image processing. But I know many visitors to this site do have that, so hopefully they can find ways to share their tips. Feel free to email me with any pretty pics/movies you make (or if you're truly desperate to play with the data but have zero idea where to start and need hints). Enjoy!
UPDATE: Just want to clarify something here: the NASA STEREO data is completely public domain data from the moment it "hits the ground", and is readily available through the NASA STEREO Science Center and the NRL SECCHI website. There's no proprietary period on it. I know several amateur astronomers that are very adept are producing animations far more beautiful than the one I did, so I strongly encourage everyone to grab that data at the earliest opportunity and play!
Keep up-to-date on the latest ISON and sungrazing comet news via my @SungrazerComets Twitter feed. All opinions stated on there, and in my blog posts, are my own.