NICER / ISS Science Nugget for March 9, 2018
SEXTANT program improves its XNAV capabilities
On March 6, 2018, the XNAV application running the SEXTANT pulsar navigation software on NICER was able to successfully run in opportunistic mode while NICER was conducting its regular science program. The science program for NICER that day included observing PSR B1937+21, which is one of the primary SEXTANT navigation pulsars.
As shown in the figure, the on-orbit XNAV application (shown in blue) was able to converge to less than 2 km of error. The same initial position (shown in red) was propagated on the ground and shown to diverge without XNAV measurements. This is a substantial improvement compared to the last pulsar navigation result from November 2017.