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Using TheSkyX Professionl to calculate the equatorial coordinates of an artificial satellite

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Jovan Skuljan Posted: 08-28-2016 8:50 PM

Hi,

I have been using TheSkyX Professional to calculate the equatorial coordinates (2000.0) of artificial Earth's satellites included in my observation project. I have noticed that the results differ slightly for the same location and observation time when I repeat the calculation after a few days, even if I use the same TLE orbital elements. Here is an example of three different sets of data I have obtained for the same satellite, Meteor 1-4 Rocket (NORAD 4394), for Mt John Observatory (New Zealand) on 26 Feb 2015 at 9:34:40 UTC:

Date of calculation             RA(2000.0)              DEC(2000.0)          Range

15 Jun 2015                  06h 41m 21.714s       -66° 46' 36.837"      569.3721
26 Aug 2016                 06h 41m 21.711s       -66° 46' 36.272"      569.3718
29 Aug 2016                 06h 41m 21.701s       -66° 46' 35.453"      569.3709

The same TLE set has been used:


1 04394U 70037B   15057.88345943  .00004958  00000-0  20115-3 0  9997
2 04394 081.2435 279.9599 0046156 108.4159 252.2100 15.23396581436441

Can you please explain why the results are different every time I make the calculation. I realise that the differences are very small and well within the accuracy of the standard SGP4 model, but I don't understand how the result is affected by the date and time when the calculation is made.

Regards,

Jovan

 

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Software Bisque Employee

Jovan Skuljan:

I have been using TheSkyX Professional to calculate the equatorial coordinates (2000.0) of artificial Earth's satellites included in my observation project. I have noticed that the results differ slightly for the same location and observation time when I repeat the calculation after a few days, even if I use the same TLE orbital elements. Here is an example of three different sets of data I have obtained for the same satellite, Meteor 1-4 Rocket (NORAD 4394), for Mt John Observatory (New Zealand) on 26 Feb 2015 at 9:34:40 UTC:

As I understand, if all is fixed, the calculations should remain consistent.  So that we can proceed,

  1. What is the exact version and build of TheSkyX?
  2. What is the exact latitude, longitude, and time zone of TheSkyX's input location?
  3. What is the exact Julian date reported by TheSkyX when the calculations are performed?

Daniel R. Bisque

Software Bisque, Inc.

862 Brickyard Circle

Golden, Colorado 80403-8058

Office Hours: 8 a.m.-5 p.m. Monday-Friday GMT-7:00

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Hi Daniel,

Sorry for a late reply. Here are the details:

1. TheSkyX Professional Edition Version 10.2.0 (Build 8461)

2. Latitude: 170 27 52.05 E, Longitude: 43 59 14.23 S, Elevation: 1018 m, Time zone: 12 h

3. Satellite JD: 2,457,079.8991

I don't know what JD was used for my previous calculations that I have already sent to you. The value listed here is from this morning, when I tried the same calculation again. By the way, is there a way to get the JD out to a higher precision?

Regards,

Jovan

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