MAST has put together the following information because it is essential for data deliveries. If the archive cannot extract the information they need from dataset headers, MAST will attempt to calculate it based on original exposures when possible. If MAST is not able to extract or calculate what it needs based on the delivered dataset headers, then some of the data will not be searchable and will not be displayed across multi-mission search results.

The following list enumerates what MAST will accept in order of preference; the links provided show the mandatory keys for that extension based on the FITS Standard v3.0 (Pence et al. 2010) paper:

1. FITS Binary Table Extension - rows and columns of data in binary representation
2. FITS ASCII Table Extension - rows and columns of data in ASCII character format

The FITS paper also provides a summary of the mandatory keywords for the above file types.

Another option is to use non-FITS, ASCII tables of catalogs (e.g. SExtractor format), which are also accepted by MAST. This format equates to the FITS Binary or ASCII Table Extension formats, but in straight ASCII files. More information is provided below.

Lastly, we will also accept CSV format, where the first line is always the list of column names, or otherwise listed in documentation.

The data format (columns) must be documented within the file itself and/or the supporting README file. For tabular, photometric catalogs in either FITS or ASCII format, we highly recommend ra, dec, flux and flux_error information (columns) per source. All columns and rows must contain data values; blanks are not allowed. For blank values, please use value 'NaN' or 'NULL' in the ASCII file, but not both within the same file. Within a data line, fields are separated by one or more whitespace characters (space or tab). A field is either a sequence of non-whitespace characters or a sequence of characters between two matching quote characters (single (') or double (") quotes) - spaces are therefore allowed in quoted fields.

SExtractor output tables are an accepted form of delivered catalogs; keywords must be in a supplemental README file or at the top of the catalog, using the designation outlined below. See SExtractor output example file with header and data to confirm allowed format. For non-SExtracor files, please follow the ASCII format outlined here.

Specification of keywords and description of the column names in the ASCII file should be done as follows:

• Use the '#' symbol to precede all keyword text lines (non-data text lines)
• The next 8 characters are used for FITS keyword name; buffer the 8-chars name with spaces (see "NAXIS" keyword in example below)
• The 9th character is an equal sign '=' followed by a at least a single space
• The keyword value can be a number or string; strings must be in single quotes
• Keyword comments are written after a "/" symbol
• The FITS 80-character line length limit applies here: no more than 79 characters in total can be used on any given line of text; the 80^th char is the end of line/return char
• The FITS "COMMENT = " keyword should be used to describe any additional information
• The "COMMENT = " keyword value is always a string within single quotes

The following is an ASCII header example of keyword, value pairs, including the 4 data column descriptions for wavelength, flux, error, and data quality. Note that these map directly onto FITS header keywords so that MAST can build FITS files from ASCII tabular spectra deliveries.

                                                           
#TELESCOP= 'HST'                / telescope used to acquire data                 
#INSTRUME= 'STIS'               / instrument used to acquire data                              
#RA_TARG =            82.586460 / right ascension of target (deg) (J2000)        
#DEC_TARG=            -7.434805 / declination of target (deg) (J2000)               
#DATE-OBS= '2003-04-28'         / UT date of start of first exposure             
#TIME-OBS= '09:20:38'           / UT start time of first exposure                
#
#XTENSION= 'BINTABLE'           /Written by IDL:  Mon May 25 12:26:32 2009       
#BITPIX  =                    8 /                                                
#NAXIS   =                    2 /Binary table                                    
#NAXIS1  =              1152000 /Number of bytes per row                         
#NAXIS2  =                    1 /Number of rows                                  
#PCOUNT  =                    0 /Random parameter count                          
#GCOUNT  =                    1 /Group count                                     
#TFIELDS =                    4 /Number of columns                               
#EXTNAME = 'E230H-2013_310X005N_52757' /Extension name                           
#EXTNO   =                    1 /Extension number                                
#TFORM1  = '64000D  '           /Real*8 (double precision)                       
#TTYPE1  = 'WAVE    '           /Column 1: Wavelength                            
#TUNIT1  = 'Angstroms'          /Units of column 1                               
#TFORM2  = '64000E  '           /Real*4 (floating point)                         
#TTYPE2  = 'FLUX    '           /Column 2: Flux Density                          
#TUNIT2  = 'erg/s/cm^2/A'       /Units of column 2                               
#TFORM3  = '64000E  '           /Real*4 (floating point)                         
#TTYPE3  = 'ERROR   '           /Column 3: Photometric Error                     
#TUNIT3  = 'erg/s/cm^2/A'       /Units of column 3                               
#TFORM4  = '64000I  '           /Integer*2 (short integer)                       
#TTYPE4  = 'DQ      '           /Column 4: Data Quality                          
#TUNIT4  = 'unitless'           /Units of column 4  
#
#COMMENT = 'Delivered to MAST from the StarCat HLSP project'
#END                                                                             

Composite data are defined as products which were constructed from other datasets.

The list of original datasets from which the dataset was made can be in the README file or provided within the dataset. Please discuss these options with MAST prior to delivery.

An example composite map from the PHAT HLSP project can be viewed within the PHAT catalog header where the "IM1*" through "IM5*" header keywords denote the observational details regarding the original 5 datasets that were used to create the catalog.

For example, a catalog can be built from a single observation with FITS keyword 'INSTRUME' = "COS". For a composite catalog made extracting fluxes from several images, say STIS and COS data, the keys would be as follows:

• INSTRUME = "MULTI"
• INSTRU01 = "COS"
• INSTRU02 = "STIS"

To designate multiple keywords, we denote this as [nn].

1. KEYWORD + KEYWORD_UNIT pair

You can specify the keyword units using a second, similar keyword where the keyword name contains the string "_UNIT" or "UNIT". Please remember to stay within the FITS 8-character keyword name limit. E.g.:

WAVECENT = 1688 / central wavelength
WAVEUNIT = angstrom / central wavelength units

2. KEYWORD = value / [unit] in brackets within the FITS comment

Comments can contain the keyword unit within brackets; this should be the first text following the standard fits comment delimiter "/", the single slash. Please remember to stay within the FITS 80-character line length limit, which includes the comments. E.g.:

RA_TARG = 2.0952854139 / [deg] right ascension of target

MAST has been ingesting and distributing HLSP data products for over 10 years. During this period, the requirements for HLSP data deliveries have expanded in order to help unify all datasets housed at MAST for ease of multi-mission searching. The example HLSP headers may not abide by all the requirements listed above because they were delivered prior to some requirements being written. We encourage the data delivery teams to provide data sample so that all header and data issues can be worked out prior to the actual delivery for ingestion into the archive.

The following projects contain many examples of catalog file headers, which can be used as a guideline for your datasets:

• FITS BINARY Table Photometric Catalog Examples
  From the The Panchromatic Hubble Andromeda Treasury (PHAT) Project:
• PHAT Catalog Header (plain text hlsp_phat_hst_wfc3-ir_12058-m31-b01-f01_f110w-f160w_v1_phot.fits header)
• PHAT Catalog FITS File (hlsp_phat_hst_wfc3-ir_12058-m31-b01-f01_f110w-f160w_v1_phot.fits from plain text header example)
From the Archive of Nearby Galaxies: Reduce, Reuse, Recycle (ANGRRR) Project:
• ANGRRR Catalog Header (plain text hlsp_angrrr_hst_wfpc2_9676-n4214-328ne-4146_f606w_v1_phot.fits header)
• ANGRRR Catalog FITS File (hlsp_angrrr_hst_wfpc2_9676-n4214-328ne-4146_f606w_v1_phot.fits from plain text header example)


• FITS ASCII Table, Catalog Example with photometric data
  From the Ultraviolet Imaging Telescope (UIT) Project holdings at MAST:
• UIT Catalog Header (plain text fuv2019aph.fits header)
• UIT Catalog FITS File with 21 (photometry) columns (fuv2019aph.fits from plain text header example)


• ASCII Table, Non-FITS Catalog Example
  From the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) Program:
• CANDELS ASCII Catalog Header + 30 rows of Data (plain text hlsp_candels_hst_wfc3_uds-tot-multiband_f160w_v1_cat_30rows.txt)
• CANDELS FITS BINARY version of entire Catalog (FITS version of file hlsp_candels_hst_wfc3_uds-tot-multiband_f160w_v1_cat.fits)
• CANDELS Catalog README (README file hlsp_candels_hst_wfc3_uds-tot-multiband_f160w_v1_readme.pdf)
Example SExtractor ASCII Catalog:
• SExtractor ASCII Catalog Header + Column Descriptors + Data (plain text example_sextractor_cat.txt)