Initial specifications and requirements for mission and the satellite bus
| Parameter | Requirements | Justification/clarification | Status |
|---|---|---|---|
| Scientific | |||
| Purpose | Observe ocean color high resolution (at best effort), on order to "zoom in" on areas of interest identified by scientists. Target area will change wrt. time of year, occurring phenomena and so on. | Firm | |
| Area of interest | Details of plumes of algae blooms | Firm | |
| Mission and payload | |||
| Observation/subject | Algae blooms | Firm | |
| Observation location | Norwegian waters, other targets of opertunity | Clarification needed: If coastal area/fjords are to be observed, how will this impact image quality? Will land pixels impact/destroy data | TBC |
| Size of area | 50 x 50 km^2 | TBC | |
| Instrument | HSI | Firm | |
FoV | The orbit altitude can range from 400 - 600 km. FoV must be adapted to this and usable resolution | TBC | |
| Resolution (spacial, time, spectral) | The orbit altitude can range from 400 - 600 km. Resolution must be calculated with these limits, and it must be determined if there are any issues/show-stoppers. Minimum daily revisit, preferably 2 or 3 passes. Technical: Depends on image data quality from slant rages Operational: Depends on cloud coverage | TBC | |
| Instrument properties | Sensitivity Number of photons SNR
| These numbers are TBC. Number of photons must be derived. Supported by data from oceanography, atmosphere physics and physical instrument properties. | TBC |
| Instrument maturity | Instrument tested and operation verified by using UAV, baloons, aircraft. | Work remains. Processing of data from UAV experiments remains in order to show proof-of-concept | TBC |
| Mechanical subsystem | |||
| Space craft size | 3U CubeSat | 2U is to small, 6U too big. 3U seems to fit all necessary subsystems, the payload and fulfill power/energy requirements | Firm |
| Payload physical envelope | Approx. 160 cm3 | Based on current model for UAVs | Reasonable estimate |
| Payload mass | 250 g (<500 g) | Based on current model for UAVs | Reasonable estimate |
| Camera aperture placement | Zenith panel S-mount | Reasonable estimate | |
| Payload material properties | Material type Thermal expansion of material The camera sensitivity wrt. thermal expansion, vibration and other disturbances | TBC. PEEK? Other advanced plastics? The satellite and payload will most likely experience large thermal gradients every pass. Data (informal) from other missions suggests that we can expect +20 C during sun illumination and -20 C during eclipse. The needed orbit will have around 30 min eclipse for every pass. Simulations must be performed | TBC |
| Power subsystem | |||
| Payload energy consumption | 3 W for 3 minutes observation pr. pass | Estimation. Target observation time expected to be shorter than 3 minutes | Reasonable estimate |
| Peak power needed | > 10 W | Should be able to operate TM/TC, downlink radio, ADCS and payload at once during target pass. | Reasonable estimate |
| Energy needed | Should be able to perform target observation (inkl. slewing maneuvering) and downlink for three consecutive passes | TBC | |
| 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 | Reasonable estimate |
| 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? Must initiate frequency allocation process | TBC |
| Downlink power/EIRP needed | Depending on GS antenna size, power available and freq. band | TBC | |
| Downlink radio energy consumption | Ground station pass expected to be 3 < t < 11 min. Max 11 min in good pass depending on orbit type (800 km). Max 8.43 min in good pass on SSO and 600 km altitude - minimum 3.33 min on 1st and 3rd pass. One downlink pass pr. target observation. 3 day revisits achievable for SSO (6 in one day), 6 day revisits with 75 deg 800 km LEO. This based on Elev. angle = 10 deg for GS. | TBC | |
| Ground station/data access | Depending on frequency band If possible, GS at NTNU, in addition to others | TBC | |
| Launch and orbit | |||
| Orbit type |
SSO mid-day//mid-night | Target area is far north, ground stations expected to be far north. Backed by scientific needs: Target of observations must be well illuminated, since the algae blooms thrive in sunlight. From available launch manifests it seems like SSO is "easy" to get, however the type of SSO is not visible in the manifest. | Firm, due to scientific needs.
|
| Orbit height | 400 - 600 km | Low orbit preferable due to better resolution, higher gives longer GS pass | Firm, due to availability of launches. |
| Orbit inclination | 75-98 deg | Referred to orbit type | |
| Other parameters | Ω: 90 - 105 deg or Ω: 270 - 285 deg
| Pass should be close to mid-day over target area for best light conditions during summer. Should be limited to ensure satellite pass by target area day-time during summer/autumn time | Reqs. firm, availability TBC |
| ADCS | |||
| Slewrate (max, precision) | Minimum: 2 deg/s Request: 4 deg/s | In order to be able to point towards target during a pass | TBC |
| Pointing accuracy | 1 deg, 0.1 deg (0.01 deg) | The higher the better, although (payload pointing) requirements may set it to even higher pointing accuracy requirement. Potential need for high (relative) accuracy during slew operation. | TBC |
| Angle requirement | Longitudinal: Max. 30 deg from Nadir. Latitudinal: Max. 46 deg from Nadir, min 32 deg from Nadir | Longitudinal requirement due to better GSD achievement
Latitudinal requirement due to observation of target on next pass (due to Earh rotation) | TBC |
| Momentum budget | Satellite must be able to perform slewing manouver for four consecutive passes | TBC | |
| Peak power needed during slew | |||
| Satellite position knowledge |