[amsat-bb] AO-7 Recent Behavior

[Bill Bordy, NJ1H]

Is it just me or did AO-07 shutdown today after working for a few minutes?

The passes I observed this on were:

26 MAY 2014 17:48 - 18:04 UTC
26 MAY 2014 19:37 - 19:57 UTC This pass in particular was a Max El of 59 
for me.

at my QTH in FN42.

73,
Bill
NJ1H


On 5/25/2014 2:42 PM, PY5LF wrote:
> Paul
> On this pass , finishing 18:43UTC ,  AO7 works all the time !
> 73
>
> PY5LF
> Luciano Fabricio
> Curitiba-PR-BR GG54jm
> http://www.qrz.com/db/PY5LF
>
> -----Mensagem original-----
> De: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] Em nome
> de Paul Stoetzer
> Enviada em: domingo, 25 de maio de 2014 12:49
> Para: amsat-bb at amsat.org
> Assunto: [amsat-bb] AO-7 Recent Behavior
>
> Good morning,
>
> AO-7 seems to be showing some odd behavior. For about three weeks of the
> eclipse cycle, it had been operating perfectly in Mode B with strong and
> clear signals on each and every pass. However, yesterday it was off during
> two ascending passes over the United States. It was back in Mode B during a
> pass over the Western United States around 23:30Z last night.
>
> PY5LF reported that it was in Mode B for 5-6 minutes after leaving eclipse
> and then it abruptly shut off. Reports from Europe on the AAR29 log also
> indicate it had shut off on ascending passes.
>
> My theory is that the sun angles on the solar panels are not ideal at this
> point. When it powers up after eclipse in Mode B, voltages fall such that
> the undervoltage detector kicks in and switches the satellite to Mode D
> (both transponders off). The satellite would then stay in Mode D until it
> loses power on the next eclipse and restarts in Mode B. If this is the case,
> my recommendation to Southern Hemisphere stations would be to wait a couple
> of minutes after it comes out of eclipse to start uplinking to the satellite
> and to keep power levels low until the panels are better illuminated.
>
> This behavior has not been reported on descending passes, though signals
> were reported to be weak and distorted at times this morning over the United
> States. Weak and distorted signals on the two meter downlink may be
> partially explained by Sporadic E as six meters has been open most of the
> morning.
>
> 73,
>
> Paul, N8HM
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