National Aeronautics and Space Administration

The X-ray Pulsar Navigation (XPNAV-1) satellite is small satellite designed and developed by the China Academy of Space Technology (CAST). It aims to observe a number of X-ray pulsar sources and develop a database of timing profiles in order to use them for navigation throughout the solar system.

XPNAV-1 was launched on November 10, 2016 from the Linquan satellite launch centre aboard a Long March 11 rocket. It was placed in a 500 km altitude low earth polar orbit (with an inclination of 97.4° and a descending node equator transit at 6 am local time). The satellite, which weighs 270 kg, is three-axis stabilized, can perform up to 90 minutes of observation on a source with one or the other of the two X-ray instruments. The mission goal is to observe as many as 26 different sources, including both isolated and binary system pulsar targets, over a five to ten year span.

The XPNAV-1 payload includes:

• Time-resolved Soft X-ray Spectometer (TSXS) which consists of a grazing incidence Wolter-I type lens of four nested mirror shells with a collection area of 30 cm² that focus X-rays onto a 15-arcmin field of view silicon drift detector (SDD). The effective detection area is 2.4 cm² at 1.5 keV. The energy range of the SDD is 0.5–10 keV with a spectral resolution of 180 eV at 5.9 keV. Timing was tracked with a GPS calibrated Rb clock with timing accuracy of events of 1.5 μs.
• High Time-resolution Proportional Counter (HTPC) consists of a collimator to narrow the field of view to 2 degrees, a microchannel plate (MCP) X-ray detector sensitive to 1–10 keV with a 1200 cm² collecting area and 100 ns timing accuracy.
• Support systems for ground communication, operations, power supply, and solar panels.

Operational constrains include turning off instruments during South Atlantic Anomaly passage to prevent damage, and keeping instruments pointed at least 45 degrees off the positions of the Sun and Moon to avoid interference.