[meteorite-list] Catalina Sky Survey
From: Mark Bowling <minador_at_meteoritecentral.com>
Date: Sun, 28 Mar 2010 22:15:20 -0700 (PDT) Message-ID: <136040.63129.qm_at_web54501.mail.re2.yahoo.com> I wouldn't think so, because I have a telescope that does that, but it isn't considered?automated.? That's how imaging is done. ----- Original Message ---- From: Shawn Alan <photophlow at yahoo.com> To: meteorite-list at meteoritecentral.com Sent: Sun, March 28, 2010 10:00:29 PM Subject: [meteorite-list] Catalina Sky Survey Richard Wow thank you for the explanation :) Do think when "they" say automated Catalina Sky Survey they mean automated from this statement you made...... "At Catalina the observer chooses the fields that will be observed and in what order, making this decision depending on the conditions, previous coverage, needs of follow up observations, etc. The telescope then observes those fields in order. Once this first set of fields has been completed, the telescope repeats the cycle three more times." Those steps to me sounds automated but again without the operator, nothing could happen at all. Here is a clip of the four images of 2008 TC3 from space of the process you just talked about. http://www.nasa.gov/images/content/321016main_D691.gif Shawn Alan [meteorite-list] Catalina Sky Survey Richard Kowalski kowalski at lpl.arizona.edu Mon Mar 29 00:29:13 EDT 2010 Previous message: [meteorite-list] On Now! - Sodom & Gomorrah on Science Channel alternate video ending Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] -------------------------------------------------------------------------------- All, I've changed the subject line to bring it in line with the discussion. As I started writing this, I thought I could get by with a simple response, but to give a clear idea of why Catalina is not an automated system, I thought I'd give you all a more detailed look at what we do each night. Sorry for the length of this response... Shawn I'll answer your query about the article first. That article is one of a line of articles all based on Jenniskens' initial and continuing misrepresentation of how we operate. I can't blame the reporters because they can only go on what they are told. "Automated" has been repeated often enough that it is becoming accepted fact. At Catalina the observer chooses the fields that will be observed and in what order, making this decision depending on the conditions, previous coverage, needs of follow up observations, etc. The telescope then observes those fields in order. Once this first set of fields has been completed, the telescope repeats the cycle three more times. Each time an image comes down from the camera our computers process the images, and then record in x-y coordinates every "object" it sees. Once all four images have been made and processed the four sets of x-y coordinates are compared with each other. The objects that are in the same locations are stars, since they haven't moved. They are ignored. Then a number of filters are run to remove groups of false detections around bright stars and "objects" that appear to be moving too fast (artificial satellites) or too slow. At the beginning of the night we download the file of the known 300,000+ minor planets from the Minor Planet Center. Our software uses this file to calculate what object should have the same position and apparent motion as the remaining suspects that are left after these filtering steps. These, along with the remaining candidates that can't be identified are are given one final calculation before the are presented to the observer for validation as an actual or false detection. This calculation assigns a number called the "Digest". The Digest is a determination that the apparent motion of the object is that of a Main Belt asteroid or not. Objects that are identified are presented at the bottom of our validation candidates. Those that have low digest numbers, representing objects that have apparent motion indicative of Main Belters, but which have not been identified, are presented in a group second from the bottom. Finally, objects which have higher digests, meaning they are not Main Belters, are presented at the top. The observer has to go through and actually look at each and every one of the candidates in this first group of detections. This could number from just a couple to 100 or more. Most of these will be marked "N" for "No" they are not real, but every so often an object is presented to the observer for validation that is real and clearly has a motion that is not typical of a main belt asteroid. Of these four observations, sometimes one or more detections may be "bad". In that case the observer can accept all four, or throw out one, two or all four observations. (You never submit a single observation). The observer also can manually measure each position to increase the accuracy of the positions. After a real object is discovered, the observer then compares the position of all known Near Earth Asteroids with the position and motion of this object to determine if it is known or not. Sometimes it is but anywhere from 1 to 10 or more times a night it is a newly discovered NEO. The observer then reports the observations to the Minor Planet Center, which posts these observations in near real time. The observer also schedules additional same night follow up observations before continuing the search for more new NEOs. We repeat this process for anywhere from 9 to 20 fields per set and up to 20 or so sets in a single night. As you can see this means we look at thousands of NEO candidates each and every night. Part of our success is we operate at a detection sigma of 1.2. Most consider a sigma of 3 a minimum to provide a reasonable Signal to Noise Ratio, but we have determined that the human eye - brain system can pull out real objects that are barely detectable above the noise level. True automated surveys don't go below 5 sigma because you can't teach a computer and software to reject false positives at such a low SNR. So, to summarize. A human determines where to observe each night, all night A human looks at each and every candidate to determine if it is real or not A human determines if all the positions are accurate or need to be remeasured. A human determines in real time if a real candidate is known or not. A human submits the observations for public dissemination in real time. A human determines if same night follow up observations need to be scheduled and accomplished. A human determines if the expected plan of observations can be followed or needs to be modified because of weather or discoveries. As one additional perk, a human determines if a candidate shows activity, going through the same process of identification, reporting, scheduling follow up, etc. By being an active candidate, I mean seeing a coma and a tail. IOW, determining the candidate is a comet. As for Petr, I could only speculate why after being informed of his error, that he would continue to minimize the efforts that it took to discover 2008 TC3 and predict its impact point down to +/- 1 kilometer so he could head out to that exact point months later to search for black rocks on white desert sand... I hope this helps explain why Catalina is not an automated survey. Richard --- On Sun, 3/28/10, Shawn Alan <photophlow at yahoo.com> wrote: > Hi Richard and List, > > That's is a great point that you brought up about the > automated Catalina Sky Survey 1.5 m telescope at Mount > Lemmon, Tucson, Arizona, and how Catalina is not an > automated survey. I wonder why they say that about her? Is > it the software that is used for Catalina or the way she > scans the sky making it automated? Or is it all done > manually these days and one by one scientist scan the sky > asteroids? > > Here is an article from 2009 that uses automated when > referring to Catalina Sky Survey.... > > > The four-meter-diameter asteroid, called 2008 TC3, was > initially sighted by the automated Catalina Sky Survey > telescope at Mount Lemmon, Ariz., on Oct. 6. Numerous > observatories, alerted to the invader, then imaged the > object. Computations correctly predicted impact would occur > 19 hours after discovery in the Nubian Desert of northern > Sudan. > > http://esciencenews.com/articles/2009/03/25/asteroid.monitored.outer.space.ground.impact > > > Shawn Alan -------------------------------------------------------------------------------- Previous message: [meteorite-list] On Now! - Sodom & Gomorrah on Science Channel alternate video ending Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] -------------------------------------------------------------------------------- More information about the Meteorite-list mailing list ______________________________________________ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list at meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list Received on Mon 29 Mar 2010 01:15:20 AM PDT |
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