SOI Logo MDI Data Availability

Here you will find information on the availability and use of MDI data, as well as a short description of the kinds of data we have available.


The Solar Oscillations Investigation will provide its data to the community of interested scholars and to the public at the earliest possible time consistent with the announced SOI Data Access & Publication Policy. Briefly, the data policy is that:

Acknowledgement and Referencing of MDI Data

If you use MDI data, please use the standard acknowledgement "SOHO is a project of international cooperation between ESA and NASA" in published papers and please reference Scherrer et al., (1995).

Descriptions of Available Data

Datasets at the SSSC are organized by Observing Program and by Level of Processing.

Observing Programs

There are five basic MDI Observing Programs, based primarily on telemetry and continuity:
Magnetic Program
Selected datasets such as individual full-disc magnetograms available in near-real time at specified intervals several times per day
Structure Program
Selected observations such as low-resolution averages that are made continuously at all times; some available in near-real time
Dynamics Program
Three sets of observations including full-disc Dopplergrams, high-resolution Dopplergrams, and full-disc intensity measurements that are made continuously for two months per year
Campaign Program
Various sets of observations made for short periods of time, usually no more than eight hours duration, when the Dynamics Program is not running
Summary Data
Selected datasets from the Magnetic Program and near-real time component of the Structure Program that are rapidly but crudely processed for purposes of mission planning

Levels of Processed Data

Data products are organized within the SOI project according to their level of processing as follows:
Raw (Telemetry)
The data as output from the MDI instrument and delivered to the SOI project by NASA. As a rule raw data are not suitable for direct analysis.
Raw data which have been decompressed and repacked into data files in the logical form delivered by the MDI instrument. Level-0 data will be stored in a standard external storage protocol, usually FITS files. For example, individual Dynamics Program Dopplergrams will be stored as individual FITS files containing the as-observed MDI velocity observable data values. Level-0 data are uncalibrated and stored in MDI instrument units.
Level-1 (Calibrated)
Level-0 data which have been calibrated into physical units of the observable, time, and physical location on the sun. The level-1 calibration process requires specific knowledge of the characteristics of the MDI instrument, of the measurement process, and of ancillary data describing the location, orientation, and motion of the SOHO spacecraft. Level-1 data are intended to be suitable for science data analysis and may be the final SOI data product for some MDI observing programs. The calibrated data constitute the fundamental permanent data archive, and they will be made publicly available after one year regardless of their use in further levels of processing.
Many helioseismology and some other science goals will require significant further processing to render the data suitable for analysis. Such processing usually involves reorganization of the data in space (mapping) or in time (frequencies). Examples of Level-2 data products are spherical harmonic amplitude time series and frequencies of solar oscillation modes for various intervals of time. These Level-2 data products are produced only as needed for the specific needs of SOI Science Working Groups and are considered to be intermediate calculations for a time determined by the working group(s) involved and described in the Investigation Plans. All Level-2 data will be made publicly available one year from the time they are provided to the requesting Science Working Groups.

Targets for SSSC Data Availability by Program

The following table lists target delays from the time of observation for the availability of datasets of different levels of processing at the SSSC. Except as otherwise noted the delays are given in days. They are targets which should seldom be exceeded. Data may become available substantially before these target times. The timing of the unrestricted release of data will be based on their actual SSSC availability rather than their targeted availability.

Observing Program Raw Level-0 Level-1 Level-2 maps Level-2 frequencies
Summary 10 min 3 hr 1
Structure 10 12 14 20 20-55
Dynamics 14 20 20 30 30-90
Magnetic 14 16 18 20
Campaigns 14 20 30 TBD TBD

General Info | Science Objectives & Proposals | Results, Images, & Documentation | Data Services & Info | Operations | Other Links | Press Releases | Solar-Center | Stanford Solar Group