Still Wrestling With Slope And Satellites

[charles phillipsParticipant]

All –

My use for DataGraph is to analyze satellites (in space) and see what they are doing. My latest effort has been to group a category of satellites and see if I can find some way to group them that helps make sense. I am using a set of satellites known as “Analyst Satellites” and trying to group them, so far this is very promising.My contention is that an orbital parameter (called RAAN) changes very regularly and can be used to group the satellites. Can I ask that people look at my first two groups and see if this makes sense? Here, if two satellites have parallel lines, they are in the same group.

I would also very much like to calculate slope and have wrestled with that, I know that I use seconds in a calculation and my slope comes out very small, I need to convert seconds to days or weeks and haven’t had a lot of luck. But I am still working on that.

Here is Group 1:

and I contend that 87071, 82698, 82205, etc are parallel and in Group 1. Clearly 89251 and 81111 are not in Group 1.

and here 81111, 89251, and 89132 are parallel and 82205 is not.

Comments?

Charles

[Jean-Yves Le StangParticipant]

Hi, Charles,

I suppose this is a follow-up to what was discussed early in June within #post-14287

I have created a small sample time series of RAAN for one Sat.

In order to get the slope:

• Create a points command from Date and RAAN columns
• In the gear menu of the Points Command select “Use in fit Command”. This will create a linear Fit Command just below the Points Command”.
• In the gear menu of this Fit Command, select “Extract as Variable/Slope. The Slope will be stored in the Global Variable Section and updated as necessary when you update te Date or the RAAN columns
• Provided the RAAN is in degrees and Date a Date column, the slope will be in degrees/second. You can just create an Expression from the slope in the Variable Section and multiply the value by the suitable factor to get the value in the required unit (here, I multiply by 86400 which is the seconds content of one day, to have the slope in Degrees/Day).
• When you have the slope of each Sat of your collection you can give to each value a Tag according to ranges of value stored in a look-up table, or filter the values using a mask.
• I don’t know if sorting the Sats by their RAAN is consistent ?

I hope it helps

[charles phillipsParticipant]

Jean-Yves –

Merci beaucoup!! let me look at this. Yes I am still working on that discussion from June, most of my time is looking at the satellite’s orbits.

Charles

 

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