The Neutron Star Interior Composition Explorer Mission


Current Activity

Requesting Targets of Opportunity (ToOs) with NICER

NICER is capable of following up on Targets of Opportunity (ToO) within 4 hours (depending on source visibility). TOO requests should be submitted via the ARK/RPS NICER Target of Opportunity/Director's Discretionary Time Request form.

The NICER team monitors the Gamma-ray Coordination Network (GCN)/Transient Astronomy Network (TAN).

Any questions regarding how to make TOO requests should be sent to the NICER Helpdesk via the HEASARC's Feedback Form.

NICER was launched aboard a SpaceX Falcon 9 rocket on June 3, 2017 at 17:07 EDT (21:07 UTC)

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.

Simulated NICER count rates and spectra can be derived using the WebPIMMS and WebSPEC tools. The Viewing tool can be used to determine the times when a specific sky position is potentially visible to NICER.

More details are availbale in NICER's Mission Guide. 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

  • NASA's NICER Catches Record-setting X-ray Burst (07 Nov 2019)
    NICER detected an intense burst of X-rays at about 10:04 p.m. EDT on Aug. 20 from a massive thermonuclear flash on the surface of the pulsar SAX J1808.4-3658. This is the brightest burst seen by NICER so far. The burst shows a remarkable two-stage evolution in flux, along with and burst oscillations at the known pulsar spin frequency.
  • NICER Background Estimator Tools (30 Oct 2019)
    Software tools to estimate background in NICER observations are under development, based on analysis of deep NICER exposures of "blank-sky" fields. "Alpha-release" versions of these tools are now available to help NICER observers better estimate backgound in observations and proposals. Understanding of the NICER background is still evolving so the estimates provided by these new tools should be used with caution.
  • NICER detection of two thermonuclear (Type I) X-ray bursts establishes that MAXI J1807+132 hosts a neutron star. (29 Oct 2019)
    NICER has detected two thermonuclear X-ray bursts from the new MAXI X-ray transient MAXI J1807+132, discovered in March 2019. The detection of these bursts show that the system is an LMXB with a neutron star primary.
  • NICER Observes X-ray Brightening of a Tidal Disruption Event Candidate (23 Oct 2019)
    NICER observations reveal that the tidal disruption candidate source AT2019azh showed a late-time brightening which perhaps indicates the formation of a transient accretion debris disk around the supermassive black hole.
  • NICER is Back in Operation (21 Oct 2019)
    NICER is operating normally after stowing for last week's ISS operations.

[More NICER News]