One of the main reasons Lady Heather tracks the sun position, calculates solar noon, etc was at the request of some people researching solar effects on the GPS signal and multipath.  You can enable logging of the satellite constellation used each second and the sun position (it shows up at sat PRN 256, the moon is PRN 257) with the W L C keyboard command.  The constellation data is output as comments in the normal log files and as <sky> data in .XML and .GPX format log files.