VonBraun Astronomical Society
Lunar Prospector Moon Pictures
Here's the cast of characters.
Anyone left out should notify me.
It all began when NASA
put up a web page describing the death of the Lunar Prospector.
http://www.ae.utexas.edu/~cfpl/lunar/ which was
to occur Saturday morning, at 4:51 CDT.
NASA just hates it when a mission is supposed to be over and all the mission scientists
beg and plead for funds because the satellite is healthy. So when someone proposed
sending the radar mapper, Magellan,
down to its death as an experiment in Venusian gas density
it received rave reviews. This started the current rage in hara-kiri satellite experiments,
and the proposal to crash the Lunar Prospector
into a permanently shadowed crater at the
Moon's south pole. There was some probability that the crash would send up a plume of
dust visible from the Earth, and an even smaller probability that water would be vaporized
from the hypothetical ice buried in this crater. Amateurs might see the dust, but spectroscopic
identification of H20 or OH would require a satellite or very dry location, which
Huntsville isn't. Mike Myszka, a student at UAH, asked if it would be possible to use the
14" Celestron at UAH Physics Dept to observe the event, and that got the ball rolling.
Clearly, the event was so short, and viewing so uncertain, the only way to get more than one
person to see the event was to take pictures of it. The university had just purchased a CCD
camera for the upcoming
solar eclipse so it looked hopeful. Unfortunately, both the location
of the UAH telescope (in the middle of well-lit parking lots) and the proximity of the
directed us to the
Von Braun Astronomical Society, located on the top of Monte Sano and
the best viewing in the area. The VBAS observatory director, Wes Swift, began to help
us prepare for the observations. All day Friday we worked on a telescope mount that would
interface to a electrically cooled CCD camera. Mitzi Adams, the VBAS planetarium director,
also managed to finagle a SBIG8 CCD camera
from MSFC as well. Friday at 5:00pm we loaded up the
van and headed up the mountain to the VBAS site, which was a good thing, it was ~100 F
down at the University.
The 16" Celestron was set up with the camera mount and as dusk was falling we booted up
the computer and cooled the camera down to operating temperatures, -20 C. This revealed
the first problem, the CCD promptly clouded up with condensed moisture. After some discussion,
Wes left for UAH to see if he could find a bottle of dry nitrogen to purge the telescope
with. I sat down in the planetarium with the SBIG8 software to see if I could learn how
to use a new camera. People I had never met before started filtering in. A few campers
from the State Park saw the lights and received my nickel tour and VBAS literature. A skunk,
the official VBAS security guard I'm told, had to be shooed out, gently.
Wes returned at 8:00 with two pizzas and some caffeinated drink, but
no dry N2. We moved on to plan B.
Setting up the SBIG8 and camera wasn't as hard as it had looked, and by now the moon had
risen above the trees. It was going on 10:00, and we had a nasty time focussing the 16",
Roy at the computer console, Wes tweaking the eyepiece focus.
As it turned out, the moon was just too bright. Wes put a piece of cardboard with a 6"
hole over the end of the telescope. We were still getting some horrendous internal reflections
that curiously looked like an eruption from the moon's south pole. I suggested we take
the picture and post it on the web calling it "preliminary", and go home. Suggestion was
overruled, our director having temporarily lost his sense of humor. This led to plan C.
After some discussion, we decided to setup the 6" Starfire refracting
telescope out on the lawn telescope mount. Joe Fikes helped set it up, but had to retire
at 11:00. Bud Martin brought a cooler full of Mountain Dew and candy bars, which kept
us going, while swatting mosquitos. Since we lacked accurate timepieces around the
observatory, Joe called in
and held his phone up to WWV radio station while our Swiss made wristwatch was calibrated.
The refractor had some balancing problems that prevented the drive from tracking the
moon, and these were solved around 12:00. It again took about an hour to get the
CCD camera focussed on a star, after an unsuccessful attempt to focus on Jupiter.
The telescope was focussed, but the CCD camera didn't have the dynamic range to handle
the moon. The shutter speed maxed out at 0.11 seconds, and the image was saturated and
bleeding into adjacent channels. Wes would have liked to put in a Barlowe expander, but
the pain of focussing prevented it. There didn't seem to be any way to avoid it, we needed
a gray filter, so Wes ran home to get some polarizing filters.
An hour later he returned with a pitcher of iced espresso and the polarizers.
Not having to actually hold
the camera, I was able to down a few espressos while balancing the notebook computer
on my lap.
With 0.11 second exposures we had pixel intensity up to 55,000 out of a maximum 65,000
(16 bit camera), which was considered awfully close. Finally we could take some pictures
of the moon. It was 3:30am. The collision would be 4:51 CDT.
We processed the images (see Moon1-7 below) and realized we had a problem, we didn't
know where we were looking. We took printouts from the WWW site above and compared them
to our pictures. We got out our Moon atlas from the VBAS library. No luck.
Apparently the illumination angle of the Sun can play tricks with
the photographs. Even the rays emanating from Tycho, which look so obvious in our
photo, were absent from the Atlas. Wes suggested that we needed to see the whole
moon to orient ourselves. So we set up his personal 14" Dobsonian reflector. I stood
on a chair and looked through the eyepiece. The amount of moonlight collected by a 14"
is indeed awesome, and I felt like I had just aligned the world's first white-laser-pointer
by eye. Stumbling down from the chair, I managed to orient our images with my good eye.
It was 4:20 and we knew where to look.
We took a picture of the moon's south pole in automatic mode, and I timed the computer.
45 seconds per frame. This just
was not going to do if the plume lasted only 15 seconds. An untried option was to narrow
the useable area of the CCD. (Moon7.jpg). Wes was doubtful, but we managed to narrow the
field of view without losing the south pole. It was now 4:45.
I fumbled with the program: automatic mode, uncompressed, no darkfield images, quarter
frame, and hit the button. It asked me for a file name, I panicked and just hit return.
It worked. The first
image went spinning to the disk, I checked my watch. 4:50:45 CDT.
Pre-impact images, used to get the calibration on the exposure as well as orient
us as to the impact site. Note that the rays are only visible at full moon, and
may not appear on all moon charts. Since they were 16 bits deep,
an 8-bit GIF file seemed inappropriate, and TIFF files were too big.
This sequence was taken as fast as the SBIG8 camera could load images onto the
hard drive. This took about 7 seconds. The image used a dark field (lens cover on)
image from the very beginning to subtract out "hot" pixels on the CCD. The impact
(based on my accurate Swiss timepiece calibrated over the telephone to WWV) nominally
occurred around AUTO002. That's because we got the automated sequence working only
one minute before impact. And you thought ARMAGEDDON was tense.
At this point, we figured we had either seen the dust cloud or it never existed. None
of our strategically placed observers on the 16" Celestron, or the 14" Dobson saw anything.
So we decided to try for the gas cloud that should persist for 15-30 minutes after impact.
Our thought was to try and get a background dark field inbetween frames. We ended up in
a mode that took 2 frames, then a darkfield, 2 frames and a darkfield. Unfortunately, the
darkfield was never written to disk, it was immediately subtracted. But that slowed down
the cadence. At the same time, the thumbscrew that held the 6" Starfire apparently
worked loose, and the tracking started to slip. You will notice that the moon seems to
rise out of the camera frame as the sequence continues. Since dawn was breaking and the
moon setting behind a large tree, we probably didn't lose any crucial data. If someone
would like to do the subtraction of images, there might still be a small chance of
observing a cloud.
The remaining files are all stored in subdirectories organized as follows:
SBIG Format Files in SBIG directory
The camera we used was a SBIG8, for Santa Barbara Instrument Group. It
came with a DOS program in the CCDOPS directory, that ran the camera
generated the files and can also manipulate the files. If you have
DOS, be sure to try out the program and let me know if it works. The
format of the files can only be read with this program, I believe.
- Pre-Impact images (Moon#.ST8)
- Impact images every 5 seconds with no dark
subtraction (AUTO.001-AUTO.024) T-1min to T+5min
- Post-Impact images with dark subtraction (T+7min to T+20min)
(AUTO.031-AUTO.070) [previously AUTO2.001-AUTO2.069] hoping to
see some evidence of the gases emitted by the impact.
SBIG DOS program in CCDOPS directory
For reading in the data files mentioned above, worked on my Pentium, and Pentium MMX
machines running in a DOS-box.
ZIPped files (pkzip) in ZIP directory
I transferred the files using the archive capability of PkZip to get chunks smaller
than 1.44 MB. These files are kept here should you want to download a slightly smaller
version of the SBIG8 format files. A bigger 900k file holds all the JPEG images too.
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