> I get this question from time to time: "how many satellites are there in > space" I know that number is huge and how many one sees is dependant on > how sharp ones eyes are, the darkness of the sky, etc., etc. > The darkness also affects which satellites are sunlit, and unless you live in the tropical zone, the length of the twilight period varies considerably with latitude, and with seasons. Latitude also affects which satellites you can see - which is one objection to using fixed sets of "bright" satellites (some are hardly visible outside lat 30-40 N/S). Some sun-synchronous objects (98 deg.inclination) that pass near noon/midnight are never seen in the tropical zone! Molnyia-type objects can be visible at 50-70 degrees S; many rockets from geosynchronous launches are only visible in a small band near the equator; others anywhere between +-30 degrees (all of those providing the perigee happens to be in the twilight zone). If you are interested in the number of visible passes, as opposed to number of unique objects, I recommend running a prediction program with a magnitude file, like SkyMap or QuickSat, or querying HeavensAbove with varying magnitude option. At higher latitudes the separation between passes in the E-W direction is smaller(also the N-S separation for orbits with visibility near their apex), and increases the number of passes of a single object in one night. The coming week, HA gives me (at +3.5 mag.) 4-8 passes in the evening, 2-5 in the morning, 10 average/night. At +4.5 mag. I get 48 passes/night. I can get to +5.0 by changing the HA URL (not on the menu), and get 98 passes/night. Moving to lat.+39, the last number increases to 144 at mag +5. (My nights are short!) For the week ending March 15, they get 78 passes, while I get 206 ! (Easy to count - and print condensed - with copy/paste of table into Excel) -- bjorn.gimle@tietotech.se (office) -- -- b_gimle@algonet.se (home) http://www.algonet.se/~b_gimle -- -- COSPAR 5919, MALMA, 59.2576 N, 18.6172 E, 23 m -- -- COSPAR 5918, HAMMARBY, 59.2985 N, 18.1045 E, 44 m -- ----------------------------------------------------------------- Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org http://www2.satellite.eu.org/sat/seesat/seesatindex.html
This archive was generated by hypermail 2b29 : Thu May 23 2002 - 08:44:57 EDT