----- Original Message ----- From: "Bob- W7LRD" w7lrd@comcast.net To: amsat-bb@amsat.org Sent: Thursday, February 25, 2010 6:07 PM Subject: [amsat-bb] future apogee calculation

Hello

Is there a "easy" way of figuring out where/when a given apogee will at a given lat.long?

73 Bob W7LRD

Hi Bob, W7LRD

Using InstantTrack it is easy but the procedure is a little bit long.

When you are in the Map Screen push F until you get a phs (phase) of 128 for AO7

At phs 128 you are at the Apogee and you can read down the map the Lat/long of the satellite subpoint at the Apogee

If you now push E you will read the keplerian elements on the map screen and if you push D you can read the derived velues at time.

To day Feb 26 we have:

Perigee Height : 1440.2 km Apogee Height : 1459.0 km Latitude of Apogee : -48.9° (South) Rate of change of Apogee: -1.866 ° / day Rate of change Argument of Perigee : - 1.957° / day

Now if you want to know the numbar of days that the apogee need to go from the actual Latitude of - 48.9° South to a wanted Latitude North you must consider that since the AO7 inclination is greater then 90° the line of the apsides that join the apogee with the perigee moves in the opposite direction of the satellite.

As an example:

If you want to know how many days the Apogee needs to go from the actual Lat of - 48.9° South to a wanted Lat of + 55.0° North the Apogee must move by 180 + (55.0 - 48.9 ) = 186.1° in the South direction so that the numbar of days needed are:

186.1° / 1.957° day = 95.09 days from February 26 i.e day 1 june 2010

If you check on any tracking program you will see that AO7 on day 1 june 2010 at 10:17 UTC will be about at phs 128 at Apogee with latitude of about + 55° North and longitude 38.0° West with the satellite subpoint at Apogee just in the middle of the Atlantic ocean.

InstantTrack is a great program if one know how to talk with him !

73" de

i8CVS Domenico