HST File Naming Convention

HST IPPPSSOOT File Name

HST data use the 'ipppssoot' file naming convention. Each letter is mapped as follows:

i : Instrument identifier; will be one of:

ppp : Program ID; can be any combination of 3 letters or numbers. There is a unique association between program ID and proposal ID (generally equivalent to the 5-digit HST phase-2 ID),

ss : Observation set ID (generally, but not always, equivalent to the HST phase-2 visit number); any combination of 2 letters or numbers.

oo : Observation number, a.k.a. 'obsnum' (generally unique for each exposure); any combination of 2 letters or numbers.

t : Source of transmission character. At launch, 't' indicated the source of the data: real time (R), tape recorder (T) or merged real time, and taped data (M). Over the years, as data ingestion has changed, the use of 't' has changed. It is simply an indicator of whether or not a better version of the data have been received. The most common sequence for the modern instruments is Q, S, where S is the retransmitted better version. The full set of possible values for 't' are:

* Note: Retransmissions between the Data Capture Facility and STScI of better versions.
** Note: Post Servicing Mission-2, all data were Q, except when a better version was sent from PACOR, and then it was S.
*** Note: For WFPC2, it started as T, changed to R, then to M a few years later, where it remained until WFPC2 was removed from HST.

'oot' Alternative : Association/product; introduced with NICMOS and STIS. These collections of exposures are created in the pre-archive pipeline and so do not need a transmission source ('t'). The three characters comprising the obsnum ('oo') and the transmission source ('t') are used to distinguish an association from an exposure. The syntax, usually represented as '0nm', allowed for products and subproducts, with '010' being the first product in a given obset (visit) and '011' being the first subproduct for that first product. An example of a subproduct is a NICMOS background exposure. Most products do not have subproducts. With the installation of ACS, the product/subproduct relation was broken as ACS designated the "prime" product, '0n0', as the dither product. Any non-dither ACS or WFC3 product is designated '0n1'.****

Note****: The '0nm' syntax is misleading as products, such as O45P01Z10, OBPW013Z0, and J8ZS0502B exist.

HST Data Suffix

HST data use a number of suffix rules after the 'ipppssoot' name.

Uncalibrated:

Calibrated:

Examples:

1. Dataset name, F05Q7407M, where 'ipppssoot' is mapped as follows:

   i=F (FGS)

   ppp=05Q

   ss=74

   oo=07

   t=M (Merged)

2. Here is an example of a NICMOS product, with two background subproducts. The subproducts are considered members of the product.

   data_set_name:	type:
   N4RK05010	PROD-TARG
   N4RK05011	PROD-BCK1
   N4RK05012	PROD-BCK2

3. ACS adopted the convention that the mn0 product would always be a dither product. Since not all ACS exposures result in a dither product, the 0n1 product is frequently the only product/association produced. Care should be taken to ensure a product is not confused with a subproduct. WFC3 continues this convention. Here is an example of an ACS repeat obs product.

   data_set_name:	type:
   J8AN01011	PROD-RPT

Additional examples and information can be found in older, html-versions of the HST Handbook and here. A full list of up-to-date HST Handbooks can be found here.