SEDSAT-2 ADCS New beginning, nov 2007
From SEDSWiki
Contents |
Passive Systems
Passive Magnetic
-Permanent Magnet and hysterisis rods
Gravity gradient boom
-Gravity gradient boom (this is a partial control system, and needs a determination system)
Provides gravity gradient stabilization on small spacecraft
- Accurate to within ±5 deg of nadir
- Used for “short” deployments (< 6m)
- High stiffness compared to tethers
- Bigger and heavier than a tether
There are 5 main boom types to consider:
- STEM Boom
- Elastic Memory Composite (EMC) Boom
- STACER Boom (SSTL)
- Coilable Booms
- Inflatable Boom
questions:
The accuracy seems to me quite high, do you happen to know about the timeframe such accuracy will be achieved? looks like there has a lot of time to pass to achieve that.....?
About the initial orientation, how do you get the boom to start prezising in the right direction? (towars or away from nadir)
Active Systems
Reaction Wheels
Momentum Wheels
Active Magnetic System
Determination: Magnetometers
Control: Magnetic Coils
Detailed documentation: http://www.cubesat.auc.dk/, http://www.ncube.no/
SWOT Analysis
| Strenghts | Weaknesses |
|---|---|
| > Often used by other CubeSats (well tested) > cheap > no moving parts | > interaction with magnetometers > not innovative > not free |
| Opportunities | Threats |
| > None | > None |
Micro propulsion system
see http://en.wikipedia.org/wiki/Pulsed_plasma_thruster for general information
Design Goals for µPPT by ARC Seibersdorf (we would get fly-ready prototypes for SEDSat):
- Impulse bit: 10-20µNs, which would guarantee a pointing accuracy of <1 degree - Spec. impulse: 500-1000 s - Power: 0,5-1,5 W - Weight: < 30g
SWOT Analysis
| Strenghts | Weaknesses |
|---|---|
| > Innovative (I think the first use with CubSat) > Very Accurate (<1°) > Electr. Prop: Can almost never run out of propellant > non-toxic propellant (Teflon) > professional manufactured devices > free | > High electr. Power Consumption (maybe up to 1,5 W per Thruster) > relatively heavy (<30g) -> only 6 thruster configuration to use |
| Opportunities | Threats |
| > Could also be used for Orbit Changes (in limits), with additional thruster(s) > PR for using an innovative new technology for CubeSat | > Not available before Fall 2008 > New Technology (first ones to test) |
Attitude determination systems
magnetometers
accelerometers
Gyroscopes
Sun sensors
Horizon sensors
Dalsa Sensors
Documentation: File:OM6802WCW5R2 071204.pdf
SWOT Analysis
| Strenghts | Weaknesses | |
|---|---|---|
| > Innovative (I think the first use with CubSat) > Accurate > professional manufactured devices > free > light weight, small volume | > Possibly High electr. Power Consumption depending on use > Have not determined precisely how they would be used | > Complicated |
| Opportunities | Threats | |
| > PR for using an innovative new technology for CubeSat | > New Technology (first ones to test in space) >need to test them to determine how we will use them > need to negotiate in order to obtain them without committing to using them. company representative currently out of office |
star trackers
discarded systems
all the system we have decided not to use
