The Neutron star Interior Composition ExploreR Mission

The Neutron star Interior Composition Explorer (NICER) is an International Space Station (ISS) payload devoted to the study of neutron stars through soft X-ray timing. Neutron stars are unique environments in which all four fundamental forces of nature are simultaneously important. They squeeze more than 1.4 solar masses into a city-size volume, giving rise to the highest stable densities known anywhere. The nature of matter under these conditions is a decades-old unsolved problem, one most directly addressed with measurements of the masses and, especially, radii of neutron stars to high precision (i.e., better than 10 percent uncertainty). With few such constraints forthcoming from observations, theory has advanced a host of models to describe the physics governing neutron star interiors; these models can be tested with astrophysical observations.

NICER will enable rotation-resolved spectroscopy of the thermal and non-thermal emissions of neutron stars in the soft (0.2-12 keV) X-ray band with unprecedented sensitivity, probing interior structure, the origins of dynamic phenomena, and the mechanisms that underlie the most powerful cosmic particle accelerators known. The NICER mission achieves these goals by deploying an X-ray timing and spectroscopy instrument on the International Space Station (ISS).

By answering a long-standing astrophysics question - How big is a neutron star? - NICER will confront nuclear physics theory with unique measurements, exploring the exotic states of matter within neutron stars through rotation-resolved X-ray spectroscopy. The capabilities that NICER brings to this investigation are unique: simultaneous fast timing and spectroscopy, with low background and high throughput. NICER will also provide continuity in X-ray-timing astrophysics more broadly, post-Rossi X-ray Timing Explorer, through a Guest Observer program. Finally, in addition to its science goals, NICER will enable the first space demonstration of pulsar-based navigation of spacecraft, through the Station Explorer for X-ray Timing and Navigation Technology (SEXTANT) enhancement to the mission, funded by the NASA Space Technology Mission Directorate's Game-Changing Development program.

NICER's X-ray Timing Instrument (XTI) represents an innovative configuration of high-heritage components. The heart of the instrument is an aligned collection of 56 X-ray "concentrator" optics (XRC) and silicon drift detector (SDD) pairs. Each XRC collects X-rays over a large geometric area from a roughly 30 arcmin2 region of the sky and focuses them onto a small SDD. The SDD detects individual photons, recording their energies with good (few percent) spectral resolution and their detection times to an unprecedented 100 nanoseconds RMS relative to Universal Time. Together, this assemblage provides a high signal-to-noise-ratio photon-counting capability within the 0.2-12 keV X-ray band, perfectly matched to the typical spectra of neutron stars as well as a broad collection of other astrophysical sources.

From NICER's ISS platform, a star-tracker-based pointing system allows the XTI to point to and track celestial targets over nearly a full hemisphere. The pointing system design accommodates the ISS vibration and contamination environments, and enables (together with NICER's GPS-based absolute timing) high-precision pulsar light-curve measurements through ultra-deep exposures spanning the 18-month mission lifetime. Anticipated launch of NICER is in early 2017.

Simulated NICER count rates and spectra can be derived using the WebPIMMS and WebSPEC tools.

A 12-slide overview of NICER science is available here.

More NICER documentation and publications.

If you would like to receive email about NICER developments, please subscribe to the NICER-announce email list.

For those interested in general astronomy/astrophysics information please go to the Education and Public Outreach site.

Artist concept of NICER

Latest News
  • NICER Passes Pre-Ship Review (25 May 2016)
    NICER has cleared another major milestone review, and the flight payload yesterday passed its Pre-Ship Review at Goddard, and will depart for Kennedy Space Center on June 7. The launch date for NICER is currently scheduled for February 1, 2017.
  • Keith Gendreau, the NICER PI, will be in a Google Hangout on March 18, 3pm EDT (16 Mar 2016)
    The AAS's "Future in Space Hangout" on March 18 at 3pm EDT will feature the CATS (Cloud-Aerosol Transport System) and NICER (Neutron star Interior Composition Explorer) payloads on the ISS, with Keith Gendreau the NICER PI participating. The hangout will address questions such as how missions are selected to run on the ISS and what the technical challenges are building instruments for operation onboard the ISS.
  • NICER Passes Pre-Environmental Review (14 Dec 2015)
    NICER has cleared another major milestone review, and the nearly-complete flight payload is poised to begin environmental (electromagnetic, vibration, thermal, etc.) testing. Delivery to NASA's Kennedy Space Center is anticipated in June 2016 for the planned August launch.
  • NICER Manifested on SpaceX-11 ISS Resupply Flight (01 Dec 2015)
    Previously scheduled for a December 2016 launch on SpaceX-12, NICER will now fly to the International Space Station with two other payloads on SpaceX Commercial Resupply Services (CRS)-11, in the Dragon vehicle's unpressurized Trunk. Launch is planned for no earlier than 15 August 2016, from Cape Canaveral Air Force Station in Florida.
  • NICER Blanketeer Featured on CBSnews (06 Jul 2015)
    Paula Cain, who makes the blanket which will protect NICER, was featured on CBSnews.com.