Re: USA 129 obs 980419

Bjoern Gimle (bjorn@tt-tech.se)
Fri, 24 Apr 1998 09:58:02 +0200

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Marco_Hahn@sl.maus.de (Marco Hahn) wrote:

> >>BG>the maneuvre appears to have been made on Apr.02, possibly around 20:26 UT.
> >>...
> >>
> >>this leads to the satellite being over Greenland at the beginning of the
> >>maneuvre, thereafter moving towards continental USA. Is this common
> practice or
> >>just a coincidence? I rather expect the first, since it's then possible to
> >>evaluate the new orbit immediately.


I can not check my computations now, but I'm pretty sure I remember correctly:

There are two key factors :

The KH's have so eccentric orbits, that the perigee practically doesn't
decrease at all. This means that a delta-v in the direction of travel
AT OR NEAR the perigee will restore the orbit to a previous condition
(in this case just a few weeks earlier)

It appears that all maneuvres I've checked so far are done AFTER the
satellite has passed within radio range from Vandenberg.
I assume they send the commands for the maneuvre just before it is
to be performed.

On Apr.2 the perigee was around 70 deg.N, going North (Greenland)
and it did pass (west of?) Vandenberg before that time.


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To: bjorn@tt-tech.se
From: b_gimle@algonet.se (Bjoern Gimle)
Subject: Re: USA 129 obs 980419
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Marco_Hahn@sl.maus.de (Marco Hahn)
>From: b_gimle@algonet.se (Bjoern Gimle)
>Subject: Re: USA 129 obs 980419
>
>
>Hej Marco!
>
>I can not check my computations now, but I'm pretty sure I remember=
 correctly:
>
>There are two key factors :
>
>The KH's have so eccentric orbits, that the perigee practically doesn't
>decrease at all. This means that a delta-v in the direction of travel
>AT OR NEAR the perigee will restore the orbit to a previous condition
>(in this case just a few weeks earlier)
>
>It appears that all maneuvres I've checked so far are done AFTER the
>satellite has passed within radio range from Vandenberg.
>I assume they send the commands for the maneuvre just before it is
>to be performed.
>
>On Apr.2 the perigee was around 70 deg.N, going North (Greenland)
>and it did pass (west of?) Vandenberg before that time.
>
>Hej d=E5,
>Bj=F6rn
>
>
>>Kommentar zu P9699@BB in der Gruppe SeeSat-Mailingliste
>>
>>Moin Bjoern,
>>
>>BG>the maneuvre appears to have been made on Apr.02, possibly around 20:26=
 UT.
>>
>>using your elset
>>
>>BG>USA 129 Apr 3-19
>>BG>1 24680U 96072  A 98108.90064327  .00027449  00000-0  27485-3 0    10
>>BG>2 24680  97.8178 169.5787 0505804  29.3849 333.4817 14.82951788    15
>>
>>this leads to the satellite being over Greenland at the beginning of the
>>maneuvre, thereafter moving towards continental USA. Is this common=20
practice or
>>just a coincidence? I rather expect the first, since it's then possible to
>>evaluate the new orbit immediately.
>>
>>Hej d=86, Marco
>>
>>
>>
>

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