UVCS/SOHO Data Policy

The following is the data access and publication policy for the SOHO
Ultraviolet Coronagraph Spectrometer Investigation.

 

I. Purpose and Statement of Data Policy

The purpose of the UVCS/SOHO data policy is to enable research in an orderly and efficient fashion while enabling the widest accessibility to the data at the earliest reasonable date. The UVCS/SOHO data policy is a UVCS implementation plan for the SOHO data access policy.

II. Access to UVCS Data

All UVCS data and data products are made available to the scientific community and the general/public within less than three months. There are no restrictions on the use of the data.

The Level-1 data (from January 1, 1996 - ninety days from the observation date) and Level-2 data (from April 1, 1996 - December 31, 2005) are available from the SOHO Archive and can also be requested from SAO.

NEW: As of October 2013, all UVCS data from the entire mission (Level-1 and Level-2) will be available immediately from the SOHO Archive.

All UVCS Co-I's, Lead Observers and Guest Investigators will have immediate access to UVCS quick look data for purposes of planning future observations and investigations.

IV. Types of UVCS Data

Within the UVCS project there are several well defined levels of processed data.

The data, as output from the UVCS instrument and delivered to the UVCS project by NASA, is called level 0 data. Level 0 data is not  useful for any purpose except processing into level-1 data.

Level-1 data is processed raw data which has been decompressed and repacked into data files in a logical form representative of the data products as delivered by the UVCS instrument. Level-1 data is stored in a standard external storage protocol (FITS files). Types of Level-1 data are the following:

  1. Spectral Data Files: These are FITS files containing uncalibrated detector count data (counts per pixel), as well as instrument configuration and exposure timing data. Each Exposure Sequence produces one Spectral Data File per detector. Each file includes a header that contains a brief, standard description for use by investigators.

  2. Visible Light Data Files: These are FITS files containing the time series of count rates from the White Light Channel, along with pointing information and information on the polarizer and neutral density filter. Each VL Data File contains the data corresponding to one exposure sequence. Each file includes a header that contains a brief, standard description for use by investigators.

Level-2 data are calibrated level-1 data which has been decompressed and are stored in a standard external storage protocol (FITS files). Types of Level-2 data are the following:

  1. Calibrated Spectral Data Files: These are FITS files containing calibrated detector intensities (photons cm -2 s-1 sr -1), as well as instrument configuration and exposure timing data. All sequential exposures in a given file for a given height, grating position and common instrument configuration are added together except in the case of Star and CME observations. Each Exposure Sequence produces one Spectral Data File per detector. Each file includes a header that contains a brief, standard description for use by investigators.

  2. Calibrated Visible Light Data Files: These are FITS files containing polarized brightness (pB) values from the White Light Channel, along with pointing information and information on the polarizer and neutral density filter. Each VL Data File contains the data corresponding to one exposure sequence. Each file includes a header that contains a brief, standard description for use by investigators.

Calibration Data Files contain the following: a) Parameter files (ascii) for pointing, spatial, wavelength and radiometric calibrations, and b) Flat field and dark count data (FITS).

Data analysis software allows the user to perform calibrations and obtain spectra that are wavelength calibrated and converted to photons cm -2 s-1 sr -1 nm-1. Calibrated pointing information can also be derived using this software. The software allows the user to write out processed spectral data files and processed visible light data files. Temporary processed spectral and visible light data files are produced at the EOF to be used as Quick Look data for observation planning. Processed data files are examples of level-2 data.

In addition, the UVCS program produces level-3 data which has undergone a higher level of processing. For example, image data files, including synoptic maps, are FITS files such as HI Ly-alpha maps of the corona that are provided as part of the Summary Data. There are also Data Catalogs to permit users to select observations based on pointing, observation date, type of feature observed, or other criteria.  They also include references to Mission Log Files, which record the observing sequences and other commands sent to the instrument. Most level-3 data will be produced by scientists in the course of analyzing the data using software and data that is publicly available.

Summary data is quick-processed Level-3 data which is available at the SOHO Experiment Operations Facility at GSFC within a few hours of receipt by the UVCS operators workstation. These data are suitable for observation planning purposes. 

The following table describes the goals for availability of the various types of data according to its purpose. 


Data Type Available to PI, Co-PI's, G-I's, A S's, and other members of Science Working Teams Available to all
Final Spectral and Visible Light Data Files < 3 months < 3 months
Calibration Files Immediately Immediately
Catalogs Immediately Immediately
Summary Data Immediately Immediately