CASSIOPE SPACECRAFT (Swarm-E)
PROCESSED DATA HANDBOOK
CAS Ephemeris Text Files
The CAS_ephemeris file is a daily product that contains spacecraft position and attitude information. It is derived from the CAS_Orbit and CAS_AttQuat files, and contains the information below. Attitude data (yaw-pitch-roll angles) are relative to the +Z-to-nadir attitude (see Coordinate Systems.)
Data:
- Year Month Day (UTC)
- Hour Minute Second (UTC)
- J2000 XGEI (km)
- J2000 YGEI (km)
- J2000 ZGEI (km)
- J2000 VXGEI (km/s)
- J2000 VYGEI (km/s)
- J2000 VZGEI (km/s)
- XGSM (km)
- YGSM (km)
- ZGSM (km)
- Geographic latitude (deg)
- Geographic longitude (deg)
- Altitude (km)
- Magnetic latitude (deg)
- Magnetic longitude (deg)
- Magnetic local time (h)
- Spacecraft attitude yaw angle (degrees)
- Spacecraft attitude pitch angle (degrees)
- Spacecraft attitude roll angle (degrees)
- Attitude Accuracy (0 = Dropout, 1 = Rough, 2 = Coarse, 3 = Moderate, 4 = Fine)
- Eclipse status
The attitude accuracy is derived from the CAS_AttQuat CDF file using each second’s ‘Time-To-Previous’ ‘Time-To-Next’, ‘Data-Source-Previous’ and ‘Data-Source-Next’.
| 0: | ‘Dropout’ is a period lacking solutions of greater than ten minutes, which is overridden with NaN. |
| 1: | ‘Rough’ is when the interpolation is between two Star-Sensor Solutions, with a total Time-between-solutions greater than 120 seconds, or that splines into or out of a solution derived from the Coarse Sun Sensors (i.e. where no star tracker solution is available) |
| 2: | ‘Coarse’ is when the interpolation is between two Star-Sensor Solutions, with a total Time-between-solutions of between 30 and 120 seconds. |
| 3: | ‘Moderate’ is when the interpolation is between two Star-Sensor Solutions, with a total Time-between-solutions of between 10 and 30 seconds. |
| 4: | ‘Fine’ is when the interpolation is between two Star-Sensor Solutions, with a total Time-between-solutions of less than 10 seconds. |
* The ‘Time-Between-Solutions’ is simply the sum of the Time-To-Prior and Time-To-Next values
* The ‘Star-Sensor Solutions’ is any solution with a Data-Source greater than 2.
Data Sources:
| 0: | Dropout (Added to indicate the start/end of a ‘NaN’ filled period) |
| 1: | Uncalibrated coarse sun sensor and magnetometer solution |
| 2: | Coarse Sun Sensors and Magnetometers |
| 3: | Onboard-fused star sensor |
| 4: | Star sensor A solution (SSA) |
| 5: | Star sensor B solution (SSB) |
| 6: | Star sensor A+B (locally fused solution) |