[amsat-bb] Satellite control via Iridium?

["Johann Lochner" <lochner@xxxxxxxxx>]

Hi folks,

FIRST OF ALL, SOME BACKGROUND INFORMATION:

In Nov. 2000 and Jan. 2001 two solar-powered weather stations, built 
by Ronald Ross, KE6JAB, and his team at Stanford, were deployed in 
Antarctica.  Originally SO-35 was used to relay data to the Internet 
(real-time and store-and-forward), but after its demise the first 
weather station could be reconfigured to digipeat via UO-22.  Since 
then the ZS7ANT station in Antarctica (designed as a control station 
for SO-35) monitored the U0-22 downlink to provide a real-time feed 
to the Internet and a daily log of all decoded data.

Data from the first station (which has so far survived two Antarctic 
winters) is still received every day.  Since it has no data relay, 
the status of the second station is unknown.  More information is at 
<http://www.thistle.org/Wx2000/>.

In Dec. 2002 a third station was deployed at yet another Antarctic 
location.  Besides weather sensors, it has a webcam and an Iridium 
modem to upload data to the Internet.  UO-22 can still be used as a 
backup relay.  More information is at <http://www.thistle.org/ANI/>.

NOW MY QUESTION, BASED ON THE SUCCESS OF THE LATEST STATION:  

How feasible is LEO satellite control via the Iridium or any other 
existing satellite constellation?

Imagine being able to access your satellite wherever it is in its 
orbit, at whatever time is convenient!  Don't have any numbers yet, 
but a quick comparison of LEO to earth-based operations led to the 
following lists of differences:

DISADVANTAGES:

* May have higher doppler shift.

* Spotty coverage due to narrower beams at orbital height (but
  remember the success of the AO-40 GPS experiments outside of
  the GPS "shell").

ADVANTAGES:

* More satellites in view.

* Closer to Iridium "shell" (less path loss cancelling spotty
  coverage to some degree).

Any additions to these lists or feedback on the importance of the 
listed factors would be much appreciated.

73 de ZR1CBC, Johann.
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