Data Products
Double Star Data Products
Fundamentals of FGM Data
The FGM instrument samples data internally at a rate of approximately 201.75 vectors/second, this is decimated by different amounts, depending on the instrument mode, which is largely dictated by the spacecraft. The following table details the most commonly used telemetry types.
| Instrument Mode | Mode Name | Primary Vectors per second | Secondary Vectors per second | |
|---|---|---|---|---|
| C | Normal Mode | 22.4 | 3.0 | Nominal mode for Spacecraft 2. |
| A | Gradiometer Mode | 12.6 | 12.6 | Nominal mode for Spacecraft 1 (used to aid removal of the interfering spacecraft magnetic field). |
| All | Housekeeping | 0.19 | 0.19 | One unfiltered 8-bit values per housekeeping packet. |
At all data rates, the data can be is returned over five different magnetic field ranges. The sensor ranges differ in the span of magnetic fields which they cover, and in their resolution, the following table details the possible ranges, and their parameters.
| Range | Maximum Range [nT] | Minimum Range [nT] | Resolution |
|---|---|---|---|
| 7 | +32764 | -32768 | 4 nT |
| 6 | +8191 | -8192.0 | 1 nT |
| 5 | +2047.75 | -2048.00 | 250 pT |
| 4 | +511.938 | -512.000 | 62.5 pT |
| 3 | +127.984 | -128.000 | 15.625 pT |
The plots below show a week of operations from June 2005, the different types of data are colour coded, so Normal Science Data is in Green, Gradiometer Mode Data is in Purple, and where nothing else is available, Housekeeping Data is shown in pale green (i.e. the instrument was in normal mode, but only returning Housekeeping). The lines at the base of the image show the ground stations used to receive the Housekeeping (HK) and Science data, Villafranca in red, and MiYun in Green.
Data Types
There are a number of different data products available, some are only used internally within the FGM operations and science teams, others are more widely available.
Prime Parameter Data Set
The Prime Parameter Data Set is spin averaged data for all the spacecraft, using the best available calibration. Normally the complete data set is only available to Co-I's and other cooperating science team members, however a subset of this data is also available from the following location:
Summary Parameter Data Set
The Summary Parameter Data Set is one minute averaged data for a single spacecraft. The Summary Parameter Data is available to anyone, but is of limited use for scientific analysis.
Both Prime and Summary Parameter Data Sets are available from your local data centre, click on the link for the Cluster Data Centers to find out which Data Center you should be using.
(Prime Parameter is available from the Data centres, but will require a username and password for access).
High Resolution Data
Some data is processed at higher rates, up to 22 vectors/second. This requires specialised calibration data, and is only done for selected parts of the data. Due to the contamination of Spacecraft 1 data by the anomalous spacecraft field, currently it is impractical to provide data at higher than spin resolution (ie Prime Parameter data). Anyone interested in Spacecraft 2 high resolution data should contact the TC-2 FGM PI Tielong Zhang for more information, if you have a requirement for high resolution science data, and wish to cooperate with the FGM Science Team on an area of study.
Processed Data can be used for science data "as-is" within the context of any caveats provided with the data.
Other Data
When none of the above data types are available, other data may be available, such as Housekeeping. Generally the fidelity of this data is much lower, and it is normally only suitable for contextual use.
Data Links:
- DoubleStar Data Centres
- UK DoubleStar Data Centre
- TC-1 FGM Principle Investigator Chris Carr
- TC-2 FGM Principle Investigator Tielong Zhang