Most of the development of IDFS is funded through various NASA contracts and grants where Dr. David Winningham is the Principal Investigator at Southwest Research Institute (SwRI) of each of the projects. Work done under NASA contract NAS8-36840 was done for Marshall Space Flight Center. Other NASA projects which support IDFS development are:

NAG5-3148, NAG5-6855, NAG5-2323, NAG5-7043

[Download IDFS Documentation]

The Instrument Data File Set (IDFS) is a set of files written in a prescribed format which contain data, timing data, and meta-data. IDFS development and evolution has been underway for the past decade, overlapping with the other storage and representation methods like CDF, HDF, and FITS. The impetus behind the IDFS is the need to maintain certain meta-data parameters with the data in order to make the displays like those in the examples possible. The two key tasks supported by the IDFS are the real-time conversion of telemetry values to engineering and scientific units as the data is accessed and the registration of each data sample to a given point in time. In magnetospheric physics, time tagging is very important because data are commonly acquired from many different sensors at the same time. Simultaneous measurements on different satellites or between a satellite and ground stations are increasingly important. Even small timing errors may completely confound a proper physical interpretation of the data.

There are three kinds of information that go into an IDFS for a given instrument: the telemetry of the sampled data, ancillary or engineering telemetry, and a large quantity of information not necessarily from the spacecraft. This last class of data can contain all sorts of calibration and timing factors. The full details are much too involved to be covered in this overview. One source of information that can be referenced in order to gain a better understanding of IDFS is the Frequently Asked Questions (FAQ) list. Given the fact that many spacecraft now have instruments that operate in nondeterministic ways due to data adaptive mode changing, the IDFS can be exceedingly detailed. However, once data is stored in an IDFS, a library of access routines allows the SDDAS to extract most any needed parameter.

The three required files within an IDFS are: data file, header file, and the virtual instrument description file (VIDF). A virtual instrument is a data stream of one measured parameter or a group of closely related parameters and it may optionally contain calibration data. The data file contains the data in its most basic form, such as telemetry values. The header file contains timing information about the data and is mainly useful when the data are non-contiguous in time. The VIDF contains text parameter descriptions, calibration tables, and a great deal more meta-data.

Additional components of the IDFS

An additional meta-file, called the Plot Information and Description File (PIDF), is used as a mechanism to further parameterize the creation of displays. This optional file contains various limit values and labels that must be associated with a particular virtual instrument. Default values are stored in the PIDF, also.

An important feature of the SDDAS is the ability to perform user-specified transformations on the data before it is displayed or plotted. The user describes each algorithm using a symbolic language that is placed in a Special Computations File (SCF). The PIDF file can then reference the SCF and the transformed data will appear as a "data source" exactly like data residing on disk. We envision a basic set of transformations being pre-coded and provided along with the SDDAS to the science community.