The geoflashers are not like tumbling rockets; to be visible at large distances they are only seen by mirror-like ("specular") reflections - more like Iridiums. But they are tumbling, uncontrolled. Ideally they are spinning like a slow gyro, and the "mirror" surfaces trace cones around the spin axis. The reflections trace cones of twice the size. This means that they are "fixed" in space and the same for all observers - except for the different position of the Sun, and the precession of the spin axis. You can only see a flash when the satellite passes near a reflection cone. SO, first an analyst must get a large number of flash observations and determine the axis position and precession, and surface cone angles. At the moment, you also depend on an analyst (or using an Excel spreadsheet I posted a year ago) to compute the flash positions. Then, you can plot your predictions on a star map and determine if the tracks cross the flash paths. I will convert my algorithm into a program that allows SkyMap to show the possible flash locations along with predictions. In the case of Superbird A, the mirror cone is almost a pole-to-pole great circle, and since all geosats move more or less on a constant declination, the flash location moves about one degree in Right Ascension per day. At the moment, Superbird A flash location RA DECREASES by 3.8 minutes/day. > Hi Rob > Sorry if these appear naive but could you tell me. What is a flash window? > Dont the geoflash sats flash all the time? How do I compute flash window and > flash location for my site? ----------------------------------------------------------------- Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org http://www.satellite.eu.org/seesat/seesatindex.html
This archive was generated by hypermail 2b29 : Fri Nov 02 2001 - 04:04:18 EST