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
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:
- Datasets are available without restrictions
as soon as they become available
at the SOI Science Support Center (SSSC).
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
There are five basic MDI Observing Programs, based primarily on telemetry
- 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
- 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.
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