I've been looking at some cosmonauts' historic accounts of missions on the Salyut series of orbital spacecraft. Characteristically they have drawn a graph of the eclipse and sunlight times of the long duration mission. The vertical axis is time after EQX of the first orbit of the day (the entry into and departure from eclipse is marked on this axis in 5 minute intervals) and the horizontal axis is the mission day.
The result is a graph in which lines extend horizontally conencting the eclipse times (both in and out), and they have characteristically filled in the darkness time with dark pen. On one print the light time has another contour with what appears to be sun angle.
The graph has then been added to by showing the plan and actual activity on that mission day.
I would find it interesting to compute a similar graph for a long duration mission of the ISS. But I have some difficulty. From a TLE I can do the following:
*calculate first eqx in utc
but can't find the time of crossing into eclipse without knowing the position of the sun and the position of the spacecraft in relation to the sun (Subsatellite point?).
Does anyone have any idea about the calculation and data involved? It must have been a hand calculation carried out by cosmonauts, but once a simple program is written I could use excel to draw the graph. Maybe a standard predictor program can produce a data output that could be rewritten into excel? I'd need the eclipse times on the orbit following the first eqx of the day.
I would appreciate any input, also any thoughts of why they would want to draw it (have only thought of observation and power).
many thanks
73 de andy G0SFJ
Hi Andy,
I've done quite a lot on eclipse study, although not quite what you are looking for.
I suggest you have a look at the SATILL package on my website www.g3cwv.co.uk . It's on the general satellite and oscar-11 pages. The program uses James Miller's PLAN10/13 routines converted to QBASIC. It should be possible to modify the code for your own requirements.
In the past I've produced a number of versions of the code, which have produced lists of data, which can be imported into a spreadsheet and plotted.
BTW the QBASIC interpreter can be freely download from the web.
I'm currently rewriting SATILL so that it runs in BBC BASIC for Windows, as this is now my preferred programming language, and allows the original PLAN10/13 routines to be run without modification.
HTH
73 Clive G3CWV
Hitchin, North Hertfordshire, UK
andy thomas wrote:
I've been looking at some cosmonauts' historic accounts of missions on the Salyut series of orbital spacecraft. Characteristically they have drawn a graph of the eclipse and sunlight times of the long duration mission. The vertical axis is time after EQX of the first orbit of the day (the entry into and departure from eclipse is marked on this axis in 5 minute intervals) and the horizontal axis is the mission day.
The result is a graph in which lines extend horizontally conencting the eclipse times (both in and out), and they have characteristically filled in the darkness time with dark pen. On one print the light time has another contour with what appears to be sun angle.
The graph has then been added to by showing the plan and actual activity on that mission day.
I would find it interesting to compute a similar graph for a long duration mission of the ISS. But I have some difficulty. From a TLE I can do the following:
*calculate first eqx in utc
but can't find the time of crossing into eclipse without knowing the position of the sun and the position of the spacecraft in relation to the sun (Subsatellite point?).
Does anyone have any idea about the calculation and data involved? It must have been a hand calculation carried out by cosmonauts, but once a simple program is written I could use excel to draw the graph. Maybe a standard predictor program can produce a data output that could be rewritten into excel? I'd need the eclipse times on the orbit following the first eqx of the day.
I would appreciate any input, also any thoughts of why they would want to draw it (have only thought of observation and power).
many thanks
73 de andy G0SFJ
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andy thomas -
Clive Wallis