The Neutron star Interior Composition ExploreR Mission

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


Post-Launch NICER activities

  • June 11 2017 NICER is extracted from the Dragon trunk
  • June 12-13 NICER is installed on the ISS ELC2
  • June14 NICER is powered up, NICER is deployed, NICER range of motion is verified by robotic camera
  • June 15 NICER executes initial Pointing control test and Detector initial checkout
  • June 17 NICER uses Raster scan of Serpens X-1 to determine X-ray instrument and star tracker alignment
  • June 21-July 12 Initial calibration and hardware commissioning
  • July 13 Begin Science Program

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.

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.

Targets of Opportunity (ToOs) Capability with NICER
NICER is capable of following up on Targets of Opportunity (ToO) within 4 hours upon receipt of request by either:

Keith Gendreau ( or Zaven Arzoumanian (

Once operations commence, the NICER team will also monitor the Gamma-ray Coordination Network (GCN)/Transient Astronomy Network (TAN).

The possibility of quicker responses than 4 hours to ToOs is currently being investigated.

Artist concept of NICER

Latest News
  • NICER First Light (17 Jul 2017)
    NASA's new Neutron star Interior Composition Explorer (NICER) mission to study the densest observable objects in the universe has begun science operations. To date, NICER has observed over 40 celestial targets to calibrate the X-ray Timing Instrument and supporting star-tracker camera. The observations also validated the payload's performance that will enable its key science measurements.
  • NICER Status Update (30 Jun 2017)
    NICER commissioning is underway. Fine alignment of the Star Tracker and X-ray Timing Instrument has been completed. The Thermal system is functioning exactly as expected. NICER has observed a number of celestial targets mostly calibration with some observations of NICER science targets.
  • NICER Installed on ELC2 (14 Jun 2017)
    As of June 14, NICER is installed on the ISS Express Logistics Carrier 2 Site 7, and power up of the instrument has begun.
  • Extraction of NICER from the Dragon Trunk (12 Jun 2017)
    This video by made by Mark Egan (MIT) shows NICER being extracted from the Dragon Trunk.
  • Upcoming NICER activities (07 Jun 2017)
    The following is the list of upcoming NICER activities and approximate dates: NICER extracted from the Dragon trunk (June 11); NICER installed on the ISS ELC2 (June 12-13); NICER powered up, deployed, and NICER range of motion verified by robotic camera (June 14); NICER executes initial Pointing control test and Detector initial checkout (June 15); NICER raster scan of Serpens X-1 to determine X-ray instrument and star tracker alignment (June 17); initial calibration and hardware commissioning (June 21-July 12); NICER science program begins (July 13)

+NICER News Archive