Initial specifications and requirements for satellite bus
| Parameter | Requirements | Justification |
|---|---|---|
| Mechanical subsystem | ||
| Payload physical envelope | Approx. 160 cm3 | Based on current model for UAVs |
| Payload mass | 250 g (<500 g) | Based on current model for UAVs |
| Camera aperture placement | Zenith panel S-mount | |
| Power subsystem | ||
| Payload energy consumption | 3 W for 3 minutes observation pr. pass | Estimation. Target observation time expected to be shorter than 3 minutes |
| Peak power needed | > 10 W | Should be able to operate TM/TC, downlink radio, ADCS and payload at once during target pass. |
| Energy needed | Should be able to perform target observation (inkl. slewing maneuvering) and downlink for four consecutive passes | |
| Communications | ||
| Downlink data rate (usable bits) | Minimum: 200 kbit/s ok Request: 1 - 2 Mbit | Estimation of size of one target measurement packet, one pr. pass: Compressed (spectral domain) S-band: X-band: 50 Mbits / 10 Mbits/sec = 5 sec 10 kanaler er typisk det vi får med komprimering i spektralt domene basert på IDLEtechs / Harald Martens teknologi. Uncompressed: 500 pixels x 500 pixels x 2 bytes/pixel x 100 channels = 50 Mbytes = 500 Mbits S-band: X-band: 500 Mbits / 10 Mbits/sec = 50 sec Attitude log information: 100 Hz gives additional 1-2 MB |
| Downlink frequency band | 2200-2290 MHz (S-band) 8025-8400 MHz (X-band) | Used for non-commercial services. Information from NRS. TBC. Must clarify which kind of license is needed. Alternative? |
| Downlink power/EIRP needed | Depending on GS antenna size, power available and freq. band | |
| Downlink radio energy consumption | Ground station pass expected to be 5 < t < 12 min. Max 12 min in good pass depending on orbit type. Max 8.43 min in good pass on SSO and 600 km altitude - minimum 3.33 min on 1st and 4th pass. One downlink pass pr. target observation. 4 revisits achievable for SSO (8 in one day), 5 revisits with 75 deg LEO. This based on Elev. angle = 10 deg for GS. | |
| Ground station/data access | Depending on frequency band If possible, GS at NTNU, in addition to others | |
| Launch and orbit | ||
| Orbit type | High-LEO/Polar (may or may not be SSO) | Target area is far north, ground stations expected to be far north |
| Orbit height | 400 - 600 km | Low orbit preferable due to better resolution, higher gives longer GS pass |
| Orbit inclination | 75-98 deg | Referred to orbit type |
| Other parameters | Ω: 30 - 45 deg or Ω: 210 - 225 deg
| Pass should be close to mid-day over target area for best light conditions Should be limited to ensure satellite pass by target area day-time during summer/autumn time |
| ADCS | ||
| Slewrate (max, precision) | Minimum: 2 deg/s Request: 4 deg/s | In order to be able to point towards target during a pass |
| Pointing accuracy | 1 deg, 0.1 deg (0.01 deg) | The higher the better, although requirements may set it to even higher pointing accuracy requirement. |
| Momentum budget | Satellite must be able to perform slewing manouver for four consecutive passes | |
| Peak power needed during slew | ||
| Satellite position knowledge |