Brian, To see ICESat laser light at this time requires a degree of determination and a fair portion of luck. To get a view of the ICESat spots like those shown at www.gsfc.nasa.gov/ topstory/2003/0920icesatfirst.html it is required to get nearly on the ground track and be under suitable clouds. This is quite hard to do at this time. Anyone more than a few hundred meters away or less will probably not see spots but may see flashes of green reflecting off of clouds much like an airport beacon or search light reflects off of low clouds. From what I have seen the observer probably needs to be within a mile or so of the ground track under ideal conditions of good clouds and darkness to see evidence of the laser beam. It will not be known how far away lit clouds can be seen until more observations are reported. I have seen ICESat illuminate clouds twice now at elevations of about 50 degrees and estimate observers with good clouds at 10,000 ft AGL may see something as much as one or two miles off- track. Getting fresh two line elements and using a good satellite tracking program with 3 decimal places of longitude output is required to get the observer within range. Here is a suggested process: First, run pass predictions out a few weeks using one of the satellite tracking programs available and chose a candidate pass close enough to suit and passing through a dark place. (Note: I think that ICESat’s laser is planned to be turned off around 12 November and turned back on March, 2004) Choosing an East-West running country road to observe from works well. Determine the latitude of the road to the nearest 0.01 degree or better. From latitude and longitude ground track data returned by the satellite tracking program determine the longitude where the ground track crosses the road to the nearest 0.05 degree or better. This may require some interpolation of the data. This crossing should be within a few miles of the best spot depending on how old your elements are and how far in the future the pass will be. It should be good enough to generally plan the trip. (Mapquest, www.mapquest.com/maps/latlong.adp is good for planning in the US at least as detailed local maps can be generated from latitude-longitude input) A day or less before the pass get as recent a two-line element set as possible and determine again the longitude of the ground track/road intersection. This time try to get the longitude of the crossing point calculated to better than 0.01 degrees. ICESat’s orbit is adjusted frequently and fresh elements are necessary to get close. Every 0.02 degree of error results in about mile of offset at 40 degrees north. I am not sure how accurate the NORAD determined elements are but I suspect they may be a significant source of error Set your watch to within a second or so of UTC. Get to the road crossing a bit before the appointed time. (This could be a chance to use that GPS receiver) Hope for some favorable atmospheric conditions, look straight up 30 seconds or so before the predicted pass and maybe something will be seen within a few seconds of the predicted pass time. Do not blink as the spots are moving 5 miles per second The above process will challenge a novice but is a great exercise in using satellite tracking tools, internet databases, land navigation skills, and experiencing the astronomer’s frustration with bad viewing conditions. In the future a more straightforward and/or accurate method may evolve if the precision orbit determination information gathered by NASA for ICESat becomes accessible. Maybe Heavens-Above could help or people involved with the “Public Outreach” portion of the ICESat program can put something together with an interactive web site. Gregg Hendry > Hi All: > > This is Brian Webb in southern California. I publish a newsletter* about > California astronomy and space news. > > My newsletter has carried info about ICESat, so the idea of observing > flashes from the ICESat laser are interesting. > > I'd like to add a one paragraph write-up on this topic for my newsletter. > Here are some questions: > > - How bright are the flashes? > > - Do you need to be at a dark site? > > - Any observing tips for beginners? > > By the way, I covered the ICESat launch from Vandenberg AFB in January. It > was great! > > Regards, > > Brian Webb > > * http://home.earthlink.net/~kd6nrp/newsletter.htm > > ----------------------------------------------------------------- > To unsubscribe from SeeSat-L, send a message with 'unsubscribe' > in the SUBJECT to SeeSat-L-request@satobs.org > List archived at http://www.satobs.org/seesat/seesatindex.html > ----------------------------------------------------------------- To unsubscribe from SeeSat-L, send a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@satobs.org List archived at http://www.satobs.org/seesat/seesatindex.html
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