Information and Links for Geotail/EPIC Data

There are two ways to get digital Geotail/EPIC data:

1. Click on this icon to launch the MIDL analysis program:

Geotail/EPIC Introduction

The Geotail spacecraft rotates with a spin axis roughly perpendicular to the ecliptic and a spin period close to 3.0 seconds. The spin is divided into 16 sectors.

The EPIC instrument consists of three sensors: ICS and STICS for ions, plus an electron detector. The ICS sensor consists of two heads, each with a 30 degree field of view. STICS has 6 heads, each with a field of view of 26.6 degrees. The electron sensor is a single head with a 60 degree field of view.

More info about the detectors (geometry factors, diagrams showing look direction, etc.) can be found at the EPIC Instrument Description Page, which has one diagram for the instrument head orientations and one for the sector arrangements. The EPIC dataset is also described further at the EPIC Science Data Center site.

The data is divided into channels, where each channel corresponds to a particular energy range of a particular species from a particular head. Sometimes a channel may include data which is "summed" over several sensor heads, meaning that counts from several heads are all included in the channel. Please read the page Geotail/EPIC Channels to learn about the many different ICS and STICS channels.

The Magnetic Field Data

Accessing Geotail/EPIC Data Through MIDL

1. The data provided in MIDL is the highest time resolution data, and therefore it can take a while to load in the tool. IF you try loading more than a few days' worth of data, your computer may run out of memory.
2. There are quite a lot of energy channels in the EPIC dataset. Please read the Geotail/EPIC Channels page, which explains the channel naming conventions and has a list defining all the channels.
3. The data is segmented into four 6 hour chunks per day starting at UT midnight. The correct number of chunks are automatically retireved no matter what time range you select, but if you want to make data loading faster, then you can only select a time range within one of the 6 hour regions.
4. MIDL provides a browsing capability to be able to view static summary images for the entire mission lifetime. There are multiple types of summary images, most of which are available online. Also, you can read about the different summary image types on the Geotail/EPIC Summary Image Description Page. The MIDL analysis tool allows you to browse any of the available types of summary images.