[amsat-bb] AO-51 update

Andrew Glasbrenner glasbrenner at mindspring.com
Sun May 2 20:08:15 PDT 2010

AO-51 has now reentered a period of eclipses that will reach almost 20 
minutes by July. Since we've been in an extended period of continuous 
illumination and very warm spacecraft temperatures, the next few weeks 
will be spent determining what the batteries capacities are now. 
Currently we are running 1.01 watt on 435.300 only, with the new PL mode 
on. For this summer eclipse season, we are fortunate that the eclipsed 
periods are while AO-51 is over mostly unoccupied Antarctica and 
surrounding areas. This means when the batteries alone are supporting 
the transmitter, there are not likely to be any users.

We have a downlink power management routine that we'll be implementing 
over the next week or so. Downlink power may range from 2 watts in 
illumination, to maybe as low as 300 milliwatts in eclipse. Using this, 
combined with the PL, should mean we can protect the batteries from 
over-discharge, while still providing the strongest possible downlink.

I'd like to encourage everyone to use the excellent reporting resource 
at http://oscar.dcarr.org/ . I check this page at least 4 times a day to 
check the status of AO-51. If the eclipse periods get too long faster 
than we can adjust, the repeater may shut off due to a low battery 
voltage watchdog. If this happens, please email me directly at 
ko4ma at amsat.org, or for those that have my cell phone number already, 
please feel free to text me a warning that the satellite repeater is off.

Additionally, the AO51-modes group would like your input on the desired 
Field Day mode. We will likely be limited to one transmitter operation. 
With AO-27, SO-50, and possibly SO-67 and HO-68 on V/U FM, S band or L/U 
operation is looking very promising to provide some variety.

Drew KO4MA
AMSAT-NA VP Operations

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