Science incoming (Converting GPS xyz to dec/RA)

[Shiro]

So BG may be an odd place to ask advice for this, but I've seen some bright minds around here and thought I'd see what kind of response I could get.

I'm working under a professor at my university who is working on tracking orbital debris. I haven't been given a formal explanation of what he's doing exactly, but from what I've gathered he's trying to study the effects of solar radiation on satellites and space junk to create better orbital models, but the measurements he needs to take are so precise that he needs to account for every possible error his method encounters to figure out whether movements observed are really being caused by the effects he's tracking, or if it's just a variation of error. So far he's got a good handle on everything but the mechanical delay on the camera shutters he's using for orbital imagery, and we're trying to come up with a way to determine it.

Our plan is to track GPS satellites and compare their observed position and time (with our scope) with their predicted/(known) time, and then take the difference between the two as the physical delay of the camera. We've found a software package online called GPS Toolkit that can parse and do fun stuff with raw GPS ephemeris data, and using logs from the NOAA we can get ephemeris data as precise as <5cm and <.01 nanoseconds, but everything we get is in an XYZ coordinate system centered at the Earth, and we need a celestial based system (Right ascension / Declination) to work with the telescopes.

My google-fu has only been able to turn up some simple calculations or formulas for converting between the two systems, but the precision we need to work at is extremely small, and most of what I've found hasn't accounted for things like geodetic variance (accounting for Earth not being a perfect circle) or differing rates of motion between the celestial and terrestrial systems. Our last resort is to take the ephemeris data we've got and make our own conversions, but there's so many variables to consider and places we could make mistakes, we're hoping we can find something like GPSTk that has already done all the work for us

Anyone know of any sort of software that would be capable of doing this or have any other suggestions? I think the biggest problem we're running into is that this kind of mechanical delay hasn't ever really been considered big enough to worry about before, probably due to most astronomical observations being focused on distant objects and rarely doing near Earth viewing, so we haven't really got anything to compare it to, and we're not even positive what variables affect it yet. Temperature? Elevation? Humidity? What the observer had for lunch?

[Vajra]

Wtf is this Astronomy or something >.>? When I read the title of this thread, I thought it was a talking about GPS systems.

[MysteryMithra]

http://i115.photobucket.com/albums/n...and_Hobbes.jpg

[Churchill]

x + y = 6 x * x = 16

make sense? just input your z data and you're good

[Shiro]

Yeah, this is astronomy. Rereading what I wrote I guess I didn't make that very clear. We're concerned with the time the mechanics in the camera in our telescope are taking to capture an image in the sky (Open / closing shutters, light entering pixels ect.). To try and figure that out we're tracking the actual GPS satellites with our telescope and using their positions to try and determine the timing involved. Converting the GPS position into something we can use, accurately, is the problem though.

, I know

[Osede]

I'm not sure what you needed. but regarding this part,

Our plan is to track GPS satellites and compare their observed position and time (with our scope) with their predicted/(known) time, and then take the difference between the two as the physical delay of the camera. We've found a software package online called GPS Toolkit that can parse and do fun stuff with raw GPS ephemeris data, and using logs from the NOAA we can get ephemeris data as precise as <5cm and <.01 nanoseconds, but everything we get is in an XYZ coordinate system centered at the Earth, and we need a celestial based system (Right ascension / Declination) to work with the telescopes.

You will only need two position reading and time difference between them then you can obtain all orbital elements. Or can just take the position and velocity data from GPS satelite's software.

Anyone know of any sort of software that would be capable of doing this or have any other suggestions? I think the biggest problem we're running into is that this kind of mechanical delay hasn't ever really been considered big enough to worry about before, probably due to most astronomical observations being focused on distant objects and rarely doing near Earth viewing, so we haven't really got anything to compare it to, and we're not even positive what variables affect it yet. Temperature? Elevation? Humidity? What the observer had for lunch?

So, is that you want to find the accuracy and compare between the measurements from camera and the gps satelite data? where the camera has some lag?

Althought I think that the professor might want to find some one who does orbit estimation that just write a simple matlab code for him with kalman filter will be enough >.>

[Gunitsoldier]

http://i115.photobucket.com/albums/n...and_Hobbes.jpg

Jesus christ lol I can never get to the part where I actually read your post because I'm stuck at laughing so hard cause of your sig.