juliensimon/nicer-observations

NICER Observation Log

Credit: NASA/JPL-Caltech

Part of a dataset collection on Hugging Face.

Dataset description

Complete NICER observation log from the HEASARC archive — every pointing made by the NICER (Neutron star Interior Composition Explorer) X-ray timing telescope mounted on the International Space Station since the instrument began science operations in mid-2017.

NICER's distinctive capability is millisecond-precision timing of soft X-ray photons (0.2-12 keV) from neutron stars, accreting binaries, magnetars, and the Sun. It has produced the most precise equation-of-state constraints on neutron-star matter to date through joint timing and spectroscopy of millisecond pulsars such as PSR J0030+0451 and PSR J0740+6620. Each row in this dataset is a single NICER pointing characterized by target, sky position, observation window, on-source exposure, the number of active focal plane modules, science category, principal investigator, and proposal-level metadata.

This dataset complements juliensimon/fermi-3pc-gamma-ray-pulsars for the same neutron-star population at GeV energies, juliensimon/swift-bat-survey and juliensimon/chandra-x-ray-sources for X-ray cross-mission searches, juliensimon/magnetars for the magnetar science category, and juliensimon/xray-binaries for the high-mass and low-mass X-ray binary populations that dominate NICER's timing program.

This dataset is suitable for tabular classification tasks.

Schema

Column	Type	Description	Sample	Null %
name	str	Target name as recorded by the NICER observation planning system (e.g. 'PSR_B1937+21', 'Crab', 'Cyg_X-1', '4U_1820-303')	Safe_mode	0.0%
ra	float64	Right ascension of the target (degrees, J2000, 0-360); zero/null for engineering and calibration pointings	0.0	0.0%
dec	float64	Declination of the target (degrees, J2000, -90 to +90)	-90.0	0.0%
lii	float64	Galactic longitude of the target (degrees, 0-360)	302.93191814	0.0%
bii	float64	Galactic latitude of the target (degrees, -90 to +90)	-27.12825126	0.0%
time	float64	Observation start time (Modified Julian Date, UTC); MJD 58239.0 corresponds to NICER mission start in 2018	59793.96875	0.0%
end_time	float64	Observation end time (Modified Julian Date, UTC)	59794.0126388889	0.0%
obsid	int64	NICER Observation ID — 10-digit identifier (e.g. '6070020809') that uniquely tags raw and reduced data products in the HEASARC archive	5001010204	0.0%
target_id	int64	Numeric target identifier from the NICER target catalog; groups observations of the same astrophysical source	-1	0.0%
target_ra	float64	Right ascension of the cataloged target (degrees, J2000); may differ slightly from ra for slewing observations	275.576333	0.4%
target_dec	float64	Declination of the cataloged target (degrees, J2000)	-16.074222	0.4%
exposure	float64	On-source exposure time in seconds, summed across all active focal plane modules; primary metric for sensitivity	0.0	0.0%
time_awarded	float64	Total exposure time awarded by the NICER Time Allocation Committee for this observation (seconds)	0.0	0.0%
num_fpm	int64	Number of focal plane modules (FPMs) returning data for this observation; NICER has 56 detectors organized in 7 modules of 8 FPMs each, with 52 nominally active	52	0.0%
processing_status	str	Pipeline processing state: 'VALIDATED' (final calibrated data ready for science), 'PROCESSED' (initial pipeline run), 'PENDING' (awaiting processing)	VALIDATED	0.0%
processing_date	float64	Date the data product was last processed (MJD UTC)	59806.8735648148	0.0%
public_date	int64	Date when the data become public after the proposal proprietary period (MJD UTC); guest observer data are typically proprietary for 1 year	59808	0.0%
prnb	int64	Proposal number (4-digit string); ties this observation to its accepted NICER guest observer or director's discretionary time proposal	5001	0.0%
abstract	str	Free-text abstract from the proposal that motivated this observation	Activities of NICER engineering team	0.0%
subject_category	str	Science category assigned by the NICER program (e.g. 'TIMING', 'MAGNETAR', 'BINARY', 'ENG', 'CALIBRATION')	ENG	0.0%
category_code	int64	Numeric science category code corresponding to subject_category	0	0.0%
pi_lname	str	Principal investigator last name	GENDREAU	0.0%
pi_fname	str	Principal investigator first name	KEITH C.	0.0%
cycle	int64	NICER observing cycle (integer); cycle 0 was the commissioning and Director's Discretionary Time phase, cycles 1+ are annual guest observer cycles	5	0.0%
obs_type	str	Observation classification: 'NOR' (normal science), 'ENG' (engineering), 'CAL' (calibration), 'DDT' (Director's Discretionary Time)	ENG	0.0%
title	str	Short title of the parent proposal (e.g. 'TIMING WORKING GROUP', 'MAGNETAR WORKING GROUP')	ENGINEERING	0.0%
galactic_nh	float64	Galactic hydrogen column density toward the target (atoms/cm^2); used for spectral fitting	1e+16	0.0%

Quick stats

• 63,866 NICER pointings since mission start in 2018
• 63,680 observations with fully validated calibrated data (processing_status = VALIDATED)
• 134.49 Ms total cumulative on-source exposure across all FPMs
• 1 distinct astrophysical targets across 9 observing cycles
• Top science categories: DIR (15,159), ACTIVE GALAXIES AND QUASARS (6,489), CAL (5,127), MAGNETAR (5,109), OSWG (5,053)

Usage

from datasets import load_dataset

ds = load_dataset("juliensimon/nicer-observations", split="train")
df = ds.to_pandas()

from datasets import load_dataset
import matplotlib.pyplot as plt

ds = load_dataset("juliensimon/nicer-observations", split="train").to_pandas()

# Total exposure per target — find NICER's most-observed sources
top = (ds.dropna(subset=["target_id"])
         .groupby(["target_id", "name"])
         .agg(total_ks=("exposure", lambda s: s.sum() / 1000),
              n_obs=("obsid", "count"))
         .sort_values("total_ks", ascending=False)
         .head(20))
print(top)

# Distribution of observations by science category
ax = ds["subject_category"].value_counts().head(10).plot(kind="barh")
ax.set_xlabel("Number of NICER observations")
ax.set_title("NICER observation volume by science category")
plt.tight_layout()
plt.show()

Data source

https://heasarc.gsfc.nasa.gov/W3Browse/all/nicermastr.html

Update schedule

Quarterly

Related datasets

• juliensimon/fermi-3pc-gamma-ray-pulsars

• juliensimon/swift-bat-hard-xray-survey

• juliensimon/chandra-x-ray-sources

• juliensimon/mcgill-magnetar-catalog

• juliensimon/xray-binary-catalog

• juliensimon/pulsar-glitch-catalog

If you find this dataset useful, please consider giving it a like on Hugging Face. It helps others discover it.

About the author

Created by Julien Simon — AI Operating Partner at Fortino Capital. Part of the Space Datasets collection.

Citation

@dataset{nicer_observations,
  title = {NICER Observation Log},
  author = {juliensimon},
  year = {2026},
  url = {https://huggingface.co/datasets/juliensimon/nicer-observations},
  publisher = {Hugging Face}
}

License

CC-BY-4.0