Power System
Power Budget (Excel Spreadsheet Format)
(Also includes "mass" and "spatial" budget for launch purposes)
(Also includes "mass" and "spatial" budget for launch purposes)
| satellite_power-mass_budget.xlsx |
Summary
When on the sunny side of the planet, the power subsystem has to be capable of charging the battery, running the satellite's CPU, camera, telemetry radio, image data transmission radio, attitude control system, and the pulsed plasma thrusters, a total worst case/peak power draw of 18.74 Watts. A more conservative estimate is 8.74 Watts, since the telemetry radio represents a maximum of 10 Watts, and should only be used occasionally for uploading commands and sending back device metrics. The 6 Watt high speed transmitter is always active in order to meet download requirements.
In the Earth's shadow, the worst case drops to 18.08 Watts, with a conservative estimate of 8.08 Watts. The primary reason for the difference is the fact that the camera is not active during transit over Earth's dark side.
Solar Panels
CubeEyes CubeSats are primarily powered from a set of four deployable solar panels attached along the short edge of the satellite body. At launch, these panels will be compactly folded against the body of the satellite; once in orbit, these spring-loaded panels will deploy at an angle of 90 degrees from the body of the satellite in a cross formation, with the solar cells pointed away from the Earth, towards the Sun.
Each of these four panels consist of seven 1.04 Watt solar cells, capable of producing a total of 29.12 Watts, more than enough to meet the theoretical worst-case power draw of 18.74 Watts (all peripherals turned on and at full power) .
Additionally, one of the two pairs of panels contains 2 out of the 3 necessary magnetorquers necessary to maintain the satellite's attitude.
Solar Panel Pair w/MTQs:
http://www.clyde-space.com/cubesat_shop/solar_panels_-_deployable/3u_deployable_solar_panels/307_3u-deployed-solar-panel-w-mtq-short-edge
"Plain" Pair of Solar Panels:
http://www.clyde-space.com/cubesat_shop/solar_panels_-_deployable/3u_deployable_solar_panels/291_3u-deployed-solar-panel-short-edge
Power Mangement and Distribution
Our CubeSats use a pair of Clyde-Space Electrical Power Systems in parallel. Each board takes in raw 16.45V (@7.29 Watts) from one of the two panel pairs, and provides regulated 3.3V and 5V power rails to the rest of the system's components. An unregulated 8.2V line direct from the battery is also provided. Both of these EPS boards feed into a distribution and overcurrent protection board.
EPS Regulation Board:
http://www.clyde-space.com/cubesat_shop/eps/337_3u-cubesat-eps
Protection/Distribution:
http://www.clyde-space.com/cubesat_shop/power_distribution_and_protection/95_cubesat-power-distribution-module
Battery:
Every 45 minutes, a given CubeSat will find itself on the dark side of the planet, away from solar energy, and will then need to rely on stored energy from the 8.2V, 20 Watt-hour battery included as part of the payload. This battery will be charged on launch, and as a result will only need partial top-up charges, (taking roughly 45 minutes in the sun), from the excess power drawn from the solar panels; otherwise, a full charge will take just under an hour and a half.
The worst case power draw from the battery is 18.08 Watts, and only excludes the camera system, (which, due to being based upon the NanoCam C1U, draws an estimated 0.66 Watts), since images will normally not be taken during transit of the dark side of the planet. As solar power will only be unavailable for about half, or 45 minutes, of the satellite's orbit, a 20 Watt-hour battery is somewhat overkill, but is the only off-the-shelf part available from our chosen supplier that meets our needs.
20 Watt-hour Rechargeable Battery:
http://www.clyde-space.com/cubesat_shop/batteries/279_cubesat-standalone-battery
When on the sunny side of the planet, the power subsystem has to be capable of charging the battery, running the satellite's CPU, camera, telemetry radio, image data transmission radio, attitude control system, and the pulsed plasma thrusters, a total worst case/peak power draw of 18.74 Watts. A more conservative estimate is 8.74 Watts, since the telemetry radio represents a maximum of 10 Watts, and should only be used occasionally for uploading commands and sending back device metrics. The 6 Watt high speed transmitter is always active in order to meet download requirements.
In the Earth's shadow, the worst case drops to 18.08 Watts, with a conservative estimate of 8.08 Watts. The primary reason for the difference is the fact that the camera is not active during transit over Earth's dark side.
Solar Panels
CubeEyes CubeSats are primarily powered from a set of four deployable solar panels attached along the short edge of the satellite body. At launch, these panels will be compactly folded against the body of the satellite; once in orbit, these spring-loaded panels will deploy at an angle of 90 degrees from the body of the satellite in a cross formation, with the solar cells pointed away from the Earth, towards the Sun.
Each of these four panels consist of seven 1.04 Watt solar cells, capable of producing a total of 29.12 Watts, more than enough to meet the theoretical worst-case power draw of 18.74 Watts (all peripherals turned on and at full power) .
Additionally, one of the two pairs of panels contains 2 out of the 3 necessary magnetorquers necessary to maintain the satellite's attitude.
Solar Panel Pair w/MTQs:
http://www.clyde-space.com/cubesat_shop/solar_panels_-_deployable/3u_deployable_solar_panels/307_3u-deployed-solar-panel-w-mtq-short-edge
"Plain" Pair of Solar Panels:
http://www.clyde-space.com/cubesat_shop/solar_panels_-_deployable/3u_deployable_solar_panels/291_3u-deployed-solar-panel-short-edge
Power Mangement and Distribution
Our CubeSats use a pair of Clyde-Space Electrical Power Systems in parallel. Each board takes in raw 16.45V (@7.29 Watts) from one of the two panel pairs, and provides regulated 3.3V and 5V power rails to the rest of the system's components. An unregulated 8.2V line direct from the battery is also provided. Both of these EPS boards feed into a distribution and overcurrent protection board.
EPS Regulation Board:
http://www.clyde-space.com/cubesat_shop/eps/337_3u-cubesat-eps
Protection/Distribution:
http://www.clyde-space.com/cubesat_shop/power_distribution_and_protection/95_cubesat-power-distribution-module
Battery:
Every 45 minutes, a given CubeSat will find itself on the dark side of the planet, away from solar energy, and will then need to rely on stored energy from the 8.2V, 20 Watt-hour battery included as part of the payload. This battery will be charged on launch, and as a result will only need partial top-up charges, (taking roughly 45 minutes in the sun), from the excess power drawn from the solar panels; otherwise, a full charge will take just under an hour and a half.
The worst case power draw from the battery is 18.08 Watts, and only excludes the camera system, (which, due to being based upon the NanoCam C1U, draws an estimated 0.66 Watts), since images will normally not be taken during transit of the dark side of the planet. As solar power will only be unavailable for about half, or 45 minutes, of the satellite's orbit, a 20 Watt-hour battery is somewhat overkill, but is the only off-the-shelf part available from our chosen supplier that meets our needs.
20 Watt-hour Rechargeable Battery:
http://www.clyde-space.com/cubesat_shop/batteries/279_cubesat-standalone-battery