[amsat-bb] Pass From The Past, continued

[Bryan Green]

Hello, all:

THIS IS A LONG POST ABOUT MY QUEST TO RESURRECT SOME OLD PASS DATA. PLEASE EXCUSE IT IF IT IS NOT OF INTEREST TO YOU.

Long story, but I have some interesting results and a theory:

1. My MP3 file is timestamped UTC as created at January 29, 2015 at 05:19. Here is some indication of that:

> ls -la *
-rwxrwxrwx@ 1 bag  staff  14289701 Jan 29 05:19 20150130T0519Z KL7CN_W6 CM98fn AO-73.mp3

2. My notes indicate that the pass occurred from 21:18 - 21:31 LOCAL time for me on January 28. This corresponds with the MP3 file timestamp, since at that time my local time was 8 hours behind UTC.

3. I have this file that I received from AMSAT by e-mail on January 23, 2015. I stripped it down to the satellite of interest:

> cat AMSAT-20150123.tle
AO-73
1 39445U 13066AF  15030.17519879  .00004024  00000-0  52953-3 0  3695
2 39445 097.7494 097.9267 0060013 224.4600 135.1787 14.79459520 62573

4. I have this QTH file defined:

> cat KL7CN_W6-CM98fn.qth 
KL7CN/W6
 38.573201
 121.529596
 7

5. With all that in mind, here is what I ran:

predict -t AMSAT-20150123.tle -q KL7CN_W6-CM98fn.qth -p AO-73 `date -u +"%s" --date="2015-01-29 05:00:00"` 

6. Here is what I get. I call this FINDING OF INTEREST #1:

1422509554 Thu 29Jan15 05:32:34    0  168  104   14  116   2987   6243  
1422509643 Thu 29Jan15 05:34:03    6  168  108   19  117   2376   6243  
1422509732 Thu 29Jan15 05:35:32   15  169  112   25  119   1777   6243  
1422509819 Thu 29Jan15 05:36:59   29  170  116   30  120   1224   6243  
1422509898 Thu 29Jan15 05:38:18   54  175  119   35  121    815   6243  
1422509952 Thu 29Jan15 05:39:12   82  211  121   38  122    683   6243  
1422509966 Thu 29Jan15 05:39:26   84  288  122   39  122    682   6243  
1422509977 Thu 29Jan15 05:39:37   79  320  122   39  122    690   6243  
1422509996 Thu 29Jan15 05:39:56   68  334  123   41  123    726   6243  
1422510031 Thu 29Jan15 05:40:31   51  341  125   43  123    847   6243  
1422510088 Thu 29Jan15 05:41:28   32  344  127   46  125   1143   6243  
1422510165 Thu 29Jan15 05:42:45   18  346  131   51  126   1620   6243  
1422510251 Thu 29Jan15 05:44:11    9  347  134   56  129   2192   6243  
1422510341 Thu 29Jan15 05:45:41    2  347  138   61  132   2799   6243  
1422510374 Thu 29Jan15 05:46:14    0  348  140   63  133   3029   6243  

NOTE: predict indicates that the AOS is 05:32.

I went with predict because it is old and very well know. I get very similar results with Orbitron and Nova for Windows, with a start time of 05:32. I get these results even when I set the PC internal clock back to January 29.

7. Here is FINDING OF INTEREST #2:

Using GoSatWatch (my go-to prediction software in the field) and using the Keps from TODAY, I get an AOS of 05:16. (It is understandably a bit off due to the Keps being a little off.) This agrees with my extemporaneous notes and the timestamp of the MP3 file.


8. Here is FINDING OF INTEREST #3:

David G0MRF very kindly provided this information using Keps from mid-March and Nova. It CONFIRMS my notes and MP3 file timestamp. I am not able to reproduce it.

Here is a link to an annotated screen capture:
http://screencast.com/t/76mfu9HLi

9. These results are inconclusive. I would LOVE to get predict to work properly with my observations.

10. My best theory: Daylight savings time confuses most satellite prediction software. GoSatWatch knows how to handle it. I wish I knew how to reproduce David's results with Nova. And I wish I could just get predict to work properly.

Any thoughts? Thanks in advance and 73!

-- bag

Bryan KL7CN/W6