Citation
Abstract
Precision measurements are now capable of determining the angular positions of spacecraft in the sky with accuracies of 2 to 5 nrad using compact radio sources having a flux density of at least a few hundred millijansky at 8.4 GHz for calibration. Further improvements in position measurement accuracy may be possible with the use of appropriate calibrators near the direction of the spacecraft even if the calibrators are much weaker (a few millijansky) in flux density. In this article, we discuss the calibrator flux density required to achieve sub-nanoradian astrometric accuracy and attempt to estimate the density of suitable calibrators, using existing source count surveys. We point out, however, that the fraction of these sources that is suitable for use as a calibrator is not well understood and requires further study.
Details
- Volume
- 42-165
- Published
- May 15, 2006
- Pages
- 1–8
- File Size
- 109.6 KB