[time-nuts] Time nuttery in space

[Jim Lux]

here's a (lengthy) paper by Todd Ely, Zaid Towfic, and Dana Sorensen about the experiments with one-way ranging on CAPSTONE (heading to the Moon).

The Iris radio had an added CSAC, and so they were able to compare performance with the raw TCXO against the CSAC against DSN's clocks, etc.

https://navi.ion.org/content/71/1/navi.633


"The Iris software radio has been updated to collect one-way Doppler and range data for potential use with deep space autonomous navigation. One-way radiometric data have found limited use because a typical radio oscillator is not sufficiently stable for use in navigation. However, Iris has been paired with a chip-scale atomic clock (CSAC) via an input signal of one pulse per second. With superior stability relative to a typical oscillator, the CSAC has the potential to provide onboard tracking data with sufficient accuracy to support a small satellite mission with modest navigation requirements. In this paper, we develop models of the Iris radio one-way Doppler and range data and analyze their performance in lab testing prior to a future inflight test on NASA’s CAPSTONE mission to the Moon. The test results confirm theoretical predictions for range precision measured between 0.38 m and 2.21 m with a range rate of 11 mm/s at 60 s."

There's a lot of discussion about where the transition from TCXO limited to CSAC limited performance is. 

Disclosure: I worked on Iris and the transition from JPL design to manufacture at SDL and had discussions early on about how to do this experiment - since I had used CSACs in another space experiment.  So I'm not exactly an unbiased observer, because it's one of my babies.Â