After observatory activation, and a calibration and a verification phase, the first NuSTAR data sets became publicly available on August 29th, 2013 through NASA's High Energy Astrophysics Science Archive Research Center (HEASARC). The second NuSTAR data release (DR2) took place on November 25th, 2013, the third (DR3) on February 5th, 2014, and the most recent (DR4) on May 7th, 2014. As of this last date, 368 NuSTAR data sets (ObsIDs) corresponding to 70 targets observed for a total exposure of 8 million seconds have been made public. NuSTAR data are most easily accessible via the usual HEASARC archive interfaces, i.e., Browse and Xamin, by querying the master table of NuSTAR data sets archived at the HEASARC, the NUMASTER table. Notice that NUMASTER contains all NuSTAR observations which have been processed and successfully validated by the NuSTAR Science Operation Center, and many of these data sets may not yet be public. Users should check the public_date parameter in NUMASTER in order to determine the public availability of observations. Proprietary data are indicated by having either a null value or a date in the future for the public_date parameter in the NUMASTER table. Users can query this table and download the data associated with the selected observation(s) using the usual Browse/Xamin procedures.
Expert users who already know the Observation IDs (ObsIDs) of the dataset(s) in which they are interested, can also directly access NuSTAR data via the HEASARC's ftp site. The public NuSTAR data are at http://heasarc.gsfc.nasa.gov/FTP/nustar/data/obs/00/ in subdirectories 0, 1, 2, 3, etc., determined by the first digit of their ObsID: thus, the data for ObsID = 80001001002 are in the directory http://heasarc.gsfc.nasa.gov/FTP/nustar/data/obs/00/8/80001001002/.
There are some known 'issues' or unusual features for a number of the released datasets. Potentially problematical issues are indicated by the parameter issue_flag in the NUMASTER table having a value set to 1. The issue_flag may indicate a value of data_gap > 0, nupsdout > 0, solar_activity is not NULL, or use of a non-standard instrument setting. The specific nature of the issue affecting the observation will be indicated in one or more non-blank or non-zero values of the following parameters in NUMASTER: data_gap, nupsdout or solar_activity, or may be indicated in the comments field for the dataset. In addition, the coordinated parameter in NUMASTER lists observatories for which coordinated observations were made with the specified NuSTAR observation. The comments parameter in NUMASTER contains a brief text synopsis of the major known issues and unusual features.
It is expected that additional datasets will be released at quarterly intervals in 2014, and that by the end of 2014 the HEASARC Archive will have 'caught up' with the available NuSTAR data. From then on, the data for a NuSTAR observation should become public no more than 60 days after the completion of that observation. The exceptions to this rule are:
a) Observations coordinated with another observatory: these will be released at
the end of the exclusive use period associated with the other observatory,