[amsat-bb] Tracking Non Earth Orbit Spacecraft......how?

Zach Leffke zleffke at vt.edu
Mon Oct 17 15:35:38 UTC 2016

Hello all,

     This might be slightly off topic, but I'm betting someone on this 
list can point me in the right direction.  I'm looking for ways to track 
spacecraft that are not in Earth Orbit (NEO?...did I just invent another 
acronym?...probably not.).  I'm trying to figure out ways to track man 
made space vehicles sent to places like the Moon, Mars, the Lagrange 
Points, and beyond.  As I understand it, TLEs + SGP4 are not the 
appropriate model for things not in the vicinity of Earth.  I'm hoping 
to find a similar technique though for looking up current orbital 
parameters for the Non-Earth satellites (like pulling TLEs from 
celestrak) in some kind of database that contains current elements for 
the spacecraft (NASA servers somewhere?), and then compute pointing 
angles from a location on earth so I can figure when and where to point 
an antenna to receive signals from these spacecraft.

I believe this may be relevant to those on this list that might be 
interested in tracking the Cube Quest Challenge amateur radio cubesat 
that will be sent to the moon in the near future.  After the trans-lunar 
injection burn, the cubesat will be ejected from the deployer.  I'd like 
to be able to track this satellite as it travels to the moon, and 
potentially help receive data from the bird's 10 GHz Downlink.  
But.......where do I point my antenna and when?

For spacecraft that are already orbiting the Moon, OK, easy enough.  
Unless the antenna has a very narrow beamwidth, I can use any 'ole EME 
tracking package to point my antenna 'at the moon' and with the 
beamwidths I'm working with, the satellite is probably in the main 
beam.  But what about the initial journey to the moon?  Also, for the 
CQC, the cubesat will not immediately enter Lunar orbit (that is where 
the 'Challenge' part comes in). So simply pointing at the Moon may not 
work reliably.

To get a little more detail......but hopefully not too much......

I like using a python module called 'pyephem' for all (well...most) 
things related to antenna pointing.  This handy module works well with 
TLE formats for Earth orbiters, contains a built in database for objects 
in the solar system, and a decent number of 'fixed' celestial objects 
like stars.  It has the ability to import new objects in the 'Xephem' 
format, for things like comets and other bodies.  If possible I'd like 
to use this feature to track other space probes like the Lunar 
Reconnaissance Orbiter, various Mars missions, Satellites at Lagrange 
Points (ACE/DISCOVR), etc. etc.

Does anyone on the list have experience with this type of thing that 
they might be willing to share?  I believe folks from AMSAT-DL 
participated in the ISEE-3 reboot mission, so how did they know when and 
where to point the Bochum antenna for this? Again, I'm looking for a 
technique that hopefully involves downloading current 'orbital 
parameters' of some standard format type (Like TLEs from celestrak, but 
for non Earth Orbiters) and then importing those parameters into pyephem 
(by possibly converting whatever gets downloaded into the 'Xephem' 
format?) in order to integrate this kind of capability into my current, 
python-based, tracking software.  Does anyone know of any publicly 
available databases that store current orbital or tracking data for 
non-earth orbiting spacecraft?  Any tutorials out there about the 
algorithms used to compute deep space spacecraft position from the 
orbital elements and thus the pointing angles (Like SGP4 + coordinate 
system math, but for non-earth orbiters)?  Any software libraries anyone 
is familiar with for this (I prefer python, but am open to other languages)?

Any and all advice, thoughts, info, papers, links, etc. would be greatly 


Zach, KJ4QLP


Research Associate
Ted & Karyn Hume Center for National Security & Technology
Virginia Polytechnic Institute & State University
Work Phone: 540-231-4174
Cell Phone: 540-808-6305

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