X/Ka-band Global Astrometric Results 

C.S. Jacobs and O.J. Sovers1

1Jet Propulsion Laboratory, Caltech/NASA

Oral presentation  

In order to extend the International Celestial Reference Frame from its S/X- band (2.3/8.4 GHz) basis to a complementary frame at X/Ka-band (8.4/32 GHz), a series of X/Ka observations acquired from 2005 to 2009 using NASA’s Deep Space Network radio telescopes. We report global astrometric results from the first 40 sessions. These sessions covered right ascension over the full 24 hours and declination down to a southern limit of ≈ −45 deg. We detected 325 sources. Of these, 314 sources had at least 2 group delay measurements which were used to produce a nearly full sky catalog with median formal position uncertainties of 200 and 350 μas in α cos(δ) and δ, respectively. An external comparison of our X/Ka-band frame to a sucessor of the S/X-band ICRF shows 306 common sources with median absolute differences of 200 μas in ∆α cos(δ) and 250 μas in ∆δ. These differences include zonal errors the largest of which are linear trends vs. declination. Systematic errors are due in part to the geometric weakness of using just two baselines and in part to mismodelling of troposphere and uncalibrated instrumental effects. Prospects for the future improvements are very positive with demonstrated technologies showing potential for a factor of three improvement in measurement precision.