Inclined Orbit

Updated 8 December 2002

Please visit  Online Satellite Calculations

 

All satellites drifts east/west and north/south in a 24 hour cyclus. Most
satellites drifts within a box of +/-0.05 degrees. Some within as little
as +/-0.01 degrees


Astra 1B over a 24H period ( figure linked from www.coolstf.com ).


With some old satellites the lifetime can be prolonged by saving fuel for orbital
north/south manouvers which result the satellite drifting in the Latitude. In the extreme some satellites
is 15 degrees inclined which means they moves inside a +/-15 degree box not a +/-0.03 degree box
like in the Astra 1B example.

Sat tracker

At http://www.lyngsat.com/tracker/europe.shtml there is sat trackers which
can show the current inclination for all satellites including the ones with
Inclined Orbit. It is imortant that the computers clock is correct. The tracker uses GMT
time which is derived from the computers local timeoffset so it's OK to use local time as long as
correect timezone is selected.

The SatTracker is developed by Rod Hewitt and the official WEB site is
located at http://www.coolstf.com/sattracker/index.html

Ephemeris parameters:

11-parameter Ephemeris data can be downloaded online for Thor ,Intelsat and NSS
satellites. The antenna pointing angles can be calculated at
http://www.satellite-calculations.com/11parameter/11parameter.htm

A 170 hour listing can be generated. Se example for Intelsat 707 - London 2.11.2002 to 9.11.2002

How to do cheap manually Inclined Orbit Tracking ?

Most motorised systems only can be controlled in the east/west direction (single axisis). This angle is called the
hourangle ( X-ANGLE on the drawing below)

If the north/east direction should be adjusted by a motor an actuator has to be installed to control the polar axis angle which
is simply the north/south direction.

An actuator can in most cases be fitted to do this job. Some welding/drilling might have to be carried out on the existing
polarmount.

The actuator can be controlled my a manually +/-36V powersupply or a positioner.

Jaeger makes polarmounts which have actuator for north/south direction. SMR1224 EL.
More Jaeger info

Some receivers like the old Chapparal Monterey 140 receiver is capable of controlling dual axis ( two actuators)
and authomaticly track the satellite based on the signal level from a defined channel. Also some old Drake analog receivers
have possibility of dual axis control.

Usually the manual tracking method works well in home systems and it also gives better performance of normal satellites if the
polarmount is not 100% correctly tracking the arc. For bigger antennas (>2m) it's nice to have manually north/south tracking
as it's more likely the polarmount will not track 100% in Ku-band..

 

Other Inclined Orbit links:
http://www.yooz.net/howcomm/InclinedOrbit.htm

 

2002 Jens T. Satre