🚀 go-pugleaf

In article <3205@kalliope.rice.edu> phil@Rice.edu (William LeFebvre) writes:
>This table includes all the windows, even those that we have missed and
>are about to miss.  A note about accuracy:  this was accurate as of
>March 9 .......
>
>Date     Open   Close   Duration
>
>4/28    13:24   13:42       18
>4/29    13:18   13:43       25
>4/30    13:13   13:44       31
>5/ 1    13:07   13:45       38
>5/ 2    13:01   13:45       44
>5/ 3    12:54   13:46       52
>5/ 4    12:48   13:47       59	[They're off! (just caught close of window)]
>5/ 5    12:42   13:48       66
>5/ 6    12:35   13:49       74
>5/ 7    12:28   13:49       81
>5/ 8    12:21   13:50       89
>5/ 9    12:11   13:51      100
>5/10    12:02   13:51      109
>5/11    11:59   13:52      113
>5/12    11:53   13:53      120
>5/13    11:46   13:47      121

From here on, the window length is 121 minutes. I presume the windows mentioned
above *would* have been 121 minutes too, but got chopped short by sunset over
at the across-the-atlantic abort sites?

In the April dates, the windows open 5 minutes earlier each day. By mid-May,
this has extended to sometimes 10 minutes a day. Why is this please? Also,
I notice that it's not a constant slippage, between May 10 & May 11 it's only
a 3-min difference, between May 8 & May 9 its 10 minutes etc.

I could understand that if the mission had to be launched so as to catch a
given sidereal time, then the window would slip by about 4 minutes a day.
This evidently isn't the case here, is it a case of launching so that the
Sun - Venus - Earth angle is the same each time or what?

Info appreciated! Thanks in Advance.
Steve

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Steve Hosgood BSc,                             | Phone (+44) 792 295213
Image Processing and Systems Engineer,         | Fax (+44) 792 295532
Institute for Industrial Information Techology,| Telex 48149
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