EIT User's Guide - Observations and Obtaining Data

Coordinating EIT Observations and Obtaining EIT data

This chapter is meant to be used as a brief guide to coordinating EIT observations and requesting and obtaining EIT data.

EIT Observing Programs

The EIT synoptic program is run with the intention of maintaining a daily survey of the state of the sun. The nominal synoptic program consists of full-field images of all four EIT wavelengths. The times of the images, the number of images and their resolution may vary from day to day.

The EIT science planner coordinates the observing sequences which are run in addition to the synoptic data. The SOHO observing targets page sometimes includes EIT subfield target coordinates and areas, image times and wavelengths, and formal observing campaigns. However, these are subject to change, and some information (such as pointing) is not available until the day of the observations, so this page isn't completely accurate. The only way to know for sure is to contact the EIT planner. The email address usually used for planners is eit@gavroc.nascom.nasa.gov

The additional observing programs which the planners coordinate are usually comprised of an EIT subfield run at a higher cadence than the full-field images. The JOP 001 movies and this movie of a macrospicule eruption are examples of this type of observation.

Planning EIT Observations

There is a separate chapter for the EIT science planners.

The best way (the only way we prefer) to plan an observing program using EIT is to contact the current EIT science planner or (if you already know the date of your proposed observations) the EIT team member who will be science planner during the intended time of the observation. You may want to put together a JOP (Joint Observing Program) if you require the participation of more than one SOHO instrument or if you are planning on coordinating an observation with a different observatory. If you plan on being a JOP leader, you should check with Bernhard Fleck and Piet Martens at jops@esa.nascom.nasa.gov for information about submitting a JOP proposal and being an effective JOP leader.

In any case, you should ensure that the EIT science planner during the dates of your observations should be fully aware of the full extent of the observing plans, and you should remain in contact with the planner until the observations are complete.

Searching for the desired EIT data

The EIT WWW catalog interface - http://umbra.nascom.nasa.gov/eit/eit-catalog.html generates a list of EIT observations according to the user's specification. As an example, this is the output for October 3 1996, for all wavelengths, and all fields of view:

  Filename                 Date          ExpoTime Wave::Filter  Image(blocks)     Image Pos(pix)    Processing Steps
 
 EFR19961003.070157   1996-Oct-03 07:01:57   15 s  284::Clear   2x(16,16) @(   1,  20/1024,1043)  Sect Seq::nomask/noocc/rice
 EFR19961003.070354   1996-Oct-03 07:03:54    1 s  195::Clear   2x(16,16) @(   1,  20/1024,1043)  Sect Seq::nomask/noocc/rice
 EFR19961003.070538   1996-Oct-03 07:05:38    5 s  304::Clear   2x(16,16) @(   1,  20/1024,1043)  Sect Seq::nomask/noocc/rice
 EFR19961003.141016   1996-Oct-03 14:10:16    3 s  171::Clear   1x( 9,14) @( 737, 180/1024, 627)  Sect Seq::nomask/noocc/rice
 EFR19961003.141122   1996-Oct-03 14:11:22   28 s  284::Clear   1x( 9,14) @( 737, 180/1024, 627)  Sect Seq::nomask/noocc/rice
 EFR19961003.141325   1996-Oct-03 14:13:25    7 s  195::Clear   1x( 9,14) @( 737, 180/1024, 627)  Sect Seq::nomask/noocc/rice
 EFR19961003.141434   1996-Oct-03 14:14:34   23 s  304::Clear   1x( 9,14) @( 737, 180/1024, 627)  Sect Seq::nomask/noocc/rice
 EFR19961003.143113   1996-Oct-03 14:31:13    3 s  171::Clear   1x( 9,14) @( 737, 180/1024, 627)  Sect Seq::nomask/noocc/rice
 EFR19961003.143219   1996-Oct-03 14:32:19   60 s  284::Clear   1x( 9,14) @( 737, 180/1024, 627)  Sect Seq::nomask/noocc/rice
 EFR19961003.143421   1996-Oct-03 14:34:21    7 s  195::Clear   1x( 9,14) @( 737, 180/1024, 627)  Sect Seq::nomask/noocc/rice
 EFR19961003.143531   1996-Oct-03 14:35:31   23 s  304::Clear   1x( 9,14) @( 737, 180/1024, 627)  Sect Seq::nomask/noocc/rice

Description:
Filename: EFR199610003.070157 - 'EFR' stands for "EIT FITS Realtime/Quicklook". The numbers preceding the period denote the date of the observation - yyyymmdd. The numbers following the period are the time of observation (in universal time) - hhmmss. 'EFZ' denotes EIT Fits Level Zero data.
Date: The date is the same as the information in the file name.
ExpoTime: The total exposure time of the image. Exposure times vary for different filters, and for the type of solar activity.
Wave::Filter: 'Wave' denotes one of the four EIT wavelengths - 171, 195, 284, and 304 Å the 'Filter' is usually in the Clear position or in the Aluminum (Al +1) position.
Image(blocks): The number preceding the 'x' is the binning of the image - 2x(16,16) means that the EIT data are binned into sets of 4 pixels (2-by-2) to reduce the size of the image. A 1024 by 1024 pixel image is thus reduced to the size of a 512 by 512 image. The second set of numbers (16x16) is the number of data blocks, with 32 pixels per block.
Image Pos(pix): The EIT pixels comprising the image. (X0,Y0/X1,Y1) A full-field image will run from the first pixel to the 1024th pixel in the x-direction, and the 20th through the 1043rd pixels in the y-direction. A partial image will have a smaller range of pixels, and will consist of a 2-dimensional array of smaller size. The nominal readout pixels are 1 to 1024 in the x-direction and 20 to 1043 in the y-direction. A subfield image listed above is as follows:

 EFR19961003.143531   1996-Oct-03 14:35:31   23 s  304::Clear   1x( 9,14) 
    @( 737, 180/1024, 627)  Sect Seq::nomask/noocc/rice

You can tell the image is a subfield because its size is 1x(9,14), 9 by 14 full-resolution blocks. The location of these blocks are 737:1024 in the x-direction (the full-res x range is 1:1024, so this subfield is far to the side of a full-resolution image) and 180:627 in the y-direction (the full-res y range is 20:1043, so this subfield is somewhere in the middle).
Processing Steps: This information is not really important - unless it signifies a "Dark" image or a "Cal Lamp," which are used to monitor EIT's detector and for calibration purposes. "rice" denotes the compression scheme that was used - this is not important, because EIT fits files are already decompressed.

Note: The level zero data, when available, is more complete than the quicklook data, and the fits headers contain more information. It is usually available about a month after the observing time. You should always try to use level zero data.

Obtaining EIT Data

The best (and honest) way to obtain EIT data is outlined in the following steps:

Determine which EIT data are available to support your study. To generate a list of available data, access the EIT WWW catalog interface - http://umbra.nascom.nasa.gov/eit/eit-catalog.html. The web catalog interface will provide a list and brief description of the data obtained over a range of dates. Keep in mind that the synoptic data and full-field images can also complement a study, so your data request needn't be restricted to a specific field of view or time cadence.
After you've isolated the files you want, click "download."
Review the EIT data rights policy, which outlines the data access and use guidelines.
Fill out a data use form so that the EIT team members can keep track of what work is being done.

Web curator: Frédéric Auchère
Responsible NASA official: Joseph B. Gurman, Facility Scientist, Solar Data Analysis Center
joseph.b.gurman@gsfc.nasa.gov
+1 301 286-4767
NASA Goddard Space Flight Center
Solar Physics Branch / Code 682

Last revised: Tuesday, December 25, 2001 2:20 PM - F. Auchère