Transcript ADCS - CubeSat

Summer Projects Review:
Current Status
ADCS
ADCS calibrated in uniform magnetic field
using support hardware to mimic the
computer onboard the satellite.
The mV/gauss change is now known:
•1-3mV/gauss for the y axis
•30-52mV/gauss for the x axis
•34-53mV/gauss for the z axis
Pointing variation for the z axis has been
calculated, α=2.891° or 0.0505C.
Current passing through the Set/Reset
strap on the HMC1053 as its resistance
changes due to the ambient temperature
has been calculated. This is directly linked
to how much power the Set/Reset will
draw.
SPACE ACADEMY
Summer Review
6th Aug. 2008
SRC
current passing through set/reset strap due to
ambient temperature
10
2.5
8
2
6
4
3 ohms
2
6 ohms
current (amps)
resistance (ohms)
set/reset strap resistance due to ambient
temperature
0
-50
1.5
1
3 ohms
0.5
6 ohms
0
0
50
100
150
-50
temperature (°C)
0
50
100
150
temperature (°C)
1.11amps
at 4.5Ω
(typical)
50 nanoseconds of peak
current (>400mA)
Set/Reset circuit
on ADCS
Set/Reset strap
on HMC1053
SPACE ACADEMY
Summer Review
6th Aug. 2008
SRC
• up to 6 solar arrays
•
1U CubeSat Electrical Power Supply
3 battery charge regulators (BCRs)
from Clyde Space
• 3 power buses, 2 regulated (3.3V and 5V) and a raw battery bus
• Bus over-current protection
• Battery under-voltage protection; if the battery voltage drops below 6.5V, the
output buses are disable until the battery voltage reaches 7.5V
PSU Main Features
• Telemetry and telecommand via an I2C bus
• Power consumption <0.1W and weight 152.96g
• Estimation of power produced when in sunlight 2.11W (solar array efficiency
17%, AM0 = 1.35kW/m2)
• Battery capacity 1.25Ah
SPACE ACADEMY
Summer Review
6th Aug. 2008
SRC
Current Status
Testing of the PSU
•
Solar array equivalent circuit and battery
simulator connected successfully
•
I2C bus has been used successfully
•
BCR1 has been damaged – testing has been
suspended
SPACE ACADEMY
Summer Review
6th Aug. 2008
SRC
GOALS
OBDH
Test flight and dev board
Incomplete
Specify physical interfaces
Complete
Set up and Software Development Environment
Complete
Write ADCS software
Incomplete
Fully interface subsystems
Incomplete
KEY FACTS
Majority of the board runs on 3.3V logic
Board includes +5V and +3.3V VCC power buses
Clock speed of MCU is 7.378 MHz
Power consumption is around 0.01 W
Mass (with physical interfaces) is 90g
Tolerances are -40 to +85°C
SPACE ACADEMY
Summer Review
6th Aug. 2008
SRC
SPACE ACADEMY
Summer Review
6th Aug. 2008
SRC
Interfacing
Physical interfaces are via the cubesat kit system bus
Multiplexing and a PowerFET are needed for the
ADCS interface.
Transceiver does not plug into the cubesat kit bus.
Modes outlined.
NORMAL OPERATING PROCEEDURE
PSU
beacon
Sunlight
Eclipse
Launch
OBDH
COMS
PAY
ADCS
CAM
Safe
SD
SPACE ACADEMY
Summer Review
6th Aug. 2008
SRC