Wednesday, February 15, 2012

ARISSat-1 Analysis - Eclipses and Elevations

Tonight, I spent some time analyzing ARISSat-1 eclipses and elevations.  I derived the location of ARISSat-1 and eclipse state from the Keplerian Elements.  I did this at five second intervals over the entire lifetime of the satellite.  I outputted the results of these calculations to a text file using the following format:

[start | finish]:  DATE  TIME  LON  LAT  ELEV  SEQ  ECLIPSE_STATE

This is a snapshot of what the first and last few records of my output file look like:


finish:  2011/8/4 18:21:17  113.762852   49.033371 371964.468750 12 0
start:   2011/8/4 19:20:37   -7.871781  -39.483602 391577.468750 12 1
finish:  2011/8/4 19:53:32   90.504473   49.075380 371938.281250 12 0
start:   2011/8/4 20:52:57  -30.867104  -39.211426 391519.281250 12 1
finish:  2011/8/4 21:25:47   67.247877   49.117396 371912.218750 12 0
start:   2011/8/4 22:25:12  -54.178058  -39.131865 391518.687500 12 1
finish:  2011/8/4 22:58:02   43.993081   49.159412 371886.250000 12 0
start:   2011/8/4 23:57:32  -77.176042  -38.856010 391459.843750 12 1
finish:  2011/8/5 00:30:27   21.651420   49.400924 371882.750000 12 0
start:   2011/8/5 01:30:07  -99.258447  -37.981538 391225.031250 12 1
...

finish:  2012/1/4 18:17:25  121.704409  -49.697238 117080.125000 4794 0
start:   2012/1/4 19:16:30  -10.982721    8.533542 106730.476562 4794 1
finish:  2012/1/4 19:44:15  101.065455  -49.408605 113319.164062 4794 0
start:   2012/1/4 20:43:10  -32.699206    8.090581 102507.820312 4794 1
finish:  2012/1/4 21:11:05   80.918078  -48.988825 109536.718750 4794 0
start:   2012/1/4 22:09:40  -54.591120    7.913555  98236.382812 4794 1
finish:  2012/1/4 22:37:45   60.295578  -48.652503 105764.578125 4794 0
start:   2012/1/4 23:36:05  -76.460252    7.733447  93970.554688 4794 1
finish:  2012/1/5 00:04:50   42.428476  -47.516509 101850.984375 4794 0
start:   2012/1/5 01:03:25  -95.938934    4.290120  90538.757812 4794 1

By doing a quick search through my output file (grep and wc for linux users :-), I was able to determine that ARISSat-1 eclipsed somewhere in the ballpark of 2415 times.

The satellites elevation changed over time, gradually diminishing towards Earths surface until it finally re-entered.  But what does this difference in elevation look like?  First, let us disregard the fact that ARISSat-1 re-entered and strictly examine the elevation data that we can derive from the Keplerian elements (using specific date/times).  To accomplish this, I chose two different transits periods, one in the early life of ARISSat and one near (or after?) it's re-entry, specifically:

2011/8/6 - 13:24:43
2012/1/4 - 00:22:30

I rendered the orbits realized after these times and then examined a common geographic location above the Equator.  You can observe these plots in the images below.  The orbit with the higher elevation occurred earlier in the life of ARISSat-1 slightly after 2011/8/6 13:24:43.  The orbit with the lower elevation may have occurred later in the life of ARISSat-1, slightly after 2012/1/4 00:22:30.  The images below provide a clear illustration of just how different the elevations were over time.

The elevation of ARISSat-1 as it passed over the Equator slightly after 13:24:43 on 2011/8/6 was approximately 381km.


The elevation of ARISSat-1 could have been roughly 166km as it passed over the Equator slightly after 00:22:30 on 2012/1/4.


The images above clearly illustrate the difference in elevation but they do not provide a good view of the overall orbit differences.  The image below provides a top-down view of the two orbits.


This final image provides a good feel for the direction ARISSat-1 was heading at these two different spans of time. 


If you would like to obtain my calculated eclipse data or if you have any questions or comments, please let me know.

1 comment:

Bruce said...

This is a wonderful visualization. Thanks!