Tuesday, August 30, 2011

Is NASA spacecraft observatory STEREO Behind HI-1 camera watching comet Elenin fade?

Over the last week or so the astronomical community has been abuzz about comet Elenin and its apparent fading as imaged from earth. Currently best observed from the Southern hemisphere, a small number of Australian observers have reported a diffusion and decrease in brightness of the inner coma. This is a sign that comet Elenin is running low on the volatiles necessary to keep it actively visible and may consequently completely lose its coma and tail. 

Meanwhile, NASA spacecraft STEREO B has been watching nonstop from the 14th to the 26th and seems to confirm this fading. I say seems, because, comet Elenin is heading away from the spacecraft very rapidly by the 24th as it heads for perihelion in just under two weeks from now. Comet Elenin appears to the HI-1 camera to be slowing down by the 24th when in fact it is speeding up. This is due to comet Elenin moving more directly away in close to a straight line and consequently this could be resulting in it becoming more and more faded in brightness. It appears brightest as it shows up in the normal field of view of the STEREO B HI-1 camera because of its range and also because of its coming out of conjunction with the sun, which causes it to light up a little more due to forward scattering. As of the 19th when a coronal mass ejection hit comet Elenin, which can be seen as a slight tail forming and then violently being ripped off and twirled about, there was a dramatic decrease in brightness and the central condensation that would normally be considered the inner coma became an elongated diffused blur as seen from earth based observers. The STEREO B HI-1 camera however is showing no decrease whatsoever in the days following the 19th, but does show a decrease by the 24th. The question is, is this due to the thermal imaging attribute of the HI-1 camera or is there something else happening? And the slight fading seen through the 24th to the 26th, can this be attributed to the rapidly increasing range or is this the actual fading that is being observed from earth? We will learn the answers in just a week or so from the time of this writing!

Saturday, August 13, 2011


2010 Perseid Meteor Shower Composite

Just kidding!  =D  There's nothing to be alarmed about!  Some doomsayers have stated that we are going to go through the debris trail of comet Elenin, we're not, but even if we were I just wanted to take a moment to say that we do that all the time.  We go through the debris trails of comets dozens of times each year.  Right now we are going through the debris trail of comet 109P Swift-Tuttle.  This happens every year at this time and is what's known as the Perseids meteor shower.  The peek activity is currently happening at the time of this writing and this meteor shower is one of the better ones that happen each year as far as the level of activity.  If you're reading this and it is nighttime wherever you are you can go out and see the meteoroids hitting the upper atmosphere right now.  The meteoroids are mainly sand sized particles from the tail of comet Swift-Tuttle.  When these meteoroids hit the atmosphere and burn up from friction we change the name to meteors and if any are big enough to make it to the ground, rare, we call them meteorites.  The moon, as you'll notice, is reflecting a lot of light right now so this will make it hard to see most of the meteors, but give it a shot and see what you can see.  I'll be out looking too, off and on tonight.  If you're in the daylight, that's ok, got ya covered with this live shot of the sky complements of NASA.

Oh, and if you're in the US and you see a sparkly light going pretty fast moving from horizon to horizon, that is not a UFO, that's the International Space Station.  =)

Tuesday, August 9, 2011

An enhanced animation from the STEREO B comet Elenin data of August 7th.

I wanted to see how it would look with the coma and tail enhanced and enlarged.  You can barely see it but comet Elenin is just starting to show a tiny tail.  =)

Friday, August 5, 2011

How to download and process your own STEREO data of comet Elenin

Just today the STEREO data for comet Elenin started being officially published and I wanted to show how and where to go to get it for those interested. The images are stored at the Solar Heliospheric Activity Research & Prediction Program section on the United States Naval Research Laboratory servers and the search form can be found here.

As you can see there are a lot of parameters that can be setup to do various kinds of searches, but we are mostly interested in comet Elenin so we can ignore most of the settings.

To set the time you can either download a whole day worth of images and look through them for comet Elenin or you can enter the time when you know the spacecraft took the images. To find the time go here, to find out what the schedule is and any changes that might have occurred. For example, in the minutes posted on August 2nd we see,

* The 135 degree rolls on Behind to observe comet Elenin started yesterday
(Aug 1). The rolls will be between 8-10 UT each day, except for Aug 5 and
Aug 12, when the rolls will be between 10-12 UT.

Ok so lets enter that time, 8 to 10 hours universal time. Notice that the day is set by default to four days in the past, that's because it takes four days for the data to be processed before it appears on the servers for downloading by the public. The first images taken of comet Elenin occurred four days ago so we do not need to set the day at the time of this writing, which is August 5th.

Then it's just a matter of setting the camera to HI-2 and the spacecraft observatory to B for behind and that's it! Clicking search brings up the images we want.

The jpegs are just small images to get an idea of how the larger fits format images will appear. What's needed next is to process the fits images into a format you can use. Fits is an image format that is well known to the scientific community. You'll want to get software that can do the processing and that can be found here.  The Fits Liberator also comes in a plugin format for Photoshop if you use one of the newer versions of Photoshop.

That should get you started finding, downloading and processing your own STEREO images nearly directly from the STEREO spacecraft.

Tuesday, August 2, 2011

Comet Elenin as imaged by NASA spacecraft STEREO B

After much planning, a spacecraft that normally looks at the sun called STEREO B was rotated downward and caught comet Elenin with one of its onboard cameras.  Comet Elenin is the fuzz ball moving in the center of the animation.

                                          This gif animation is in the public domain

STEREO B is one of two NASA spacecraft launched on October 26, 2006 to study the daily activity of the sun.  STEREO is an acronym for Solar TErrestrial RElations Observatory.  These two spacecraft obit along with the earth at the same distance from the sun as earth, one about three months ahead of earth and one about three months behind earth.  STEREO A is ahead of earth and STEREO B is following behind earth.

Purely by chance, comet Elenin on its inbound leg is currently passing very close to STEREO B and so NASA took advantage of this and pointed this spacecraft to look at comet Elenin as it is passing by.  Comet Elenin is going to start picking up speed as it swings around the sun and we will get to watch its tail develop as it does so on the various STEREO cameras.  For updates and more information go here:  http://stereo.gsfc.nasa.gov/gallery/item.php?id=selects&iid=154