The current Sapling concept of operations consists of just two high level modes or phases: “idle” and “low power mode.”
While in idle mode, Sapling transmits a beacon every 60 seconds (time interval configurable) and then waits for a response from the ground station. All onboard spacecraft systems are enabled during idle mode.
While in low power mode, the spacecraft disables the motor drivers, neopixel, radio, coral, IMU, ambient light sensors, and GPS in an effort to minimize power consumption. After entering low power mode, the spacecraft is configured to “wake up” after 60 minutes, run data collection tasks, beacon, check if it satisfies the low power mode exit criteria, and either return to low power mode or move into idle mode.
| Requirement | Parameter | Description | Parent(s) |
|---|---|---|---|
| OPS-101 | Idle mode | The spacecraft shall possess one operational mode during which each subsystem is enabled. | SYS-101, SYS-102, SYS-301, SYS-401, SYS-402 |
| This mode is needed to ensure the technology demonstration goals are achievable. | |||
| OPS-102 | Low power mode | The spacecraft shall possess one operational mode that is net orbit average power positive with worst case maximum solar power assumptions | SYS-501 |
| This mode is needed to ensure that the spacecraft stays alive for its operational lifetime. | |||
| OPS-201 | SOC < 65% | The spacecraft shall enter low power mode when state of charge is very low. | OPS-102 |
| This condition constitutes the low SOC low power mode entry criteria. | |||
| OPS-202 | SOC > 73% | The spacecraft shall exit low power mode when state of charge has increased. | OPS-101 |
| This condition constitutes the low SOC low power mode exit criteria. | |||
| OPS-301 | CPU Temp < -30ºC; | ||
| OR | |||
| Battery temp < -20ºC | The spacecraft shall enter low power mode when CPU or battery temperature is below operational conditions. | OPS-102 | |
| These conditions constitute the very low temperature low power mode entry criteria. | |||
| OPS-302 | CPU Temp > -25ºC | ||
| AND | |||
| Battery Temp > -15ºC | The spacecraft shall exit low power mode when CPU and battery temperature are within operational range with margin. | OPS-101 | |
| These conditions constitute the very low temperature low power mode exit criteria. | |||
| OPS-303 | CPU Temp > 80ºC | ||
| OR | |||
| Battery Temp > 60ºC | The spacecraft shall enter low power mode when battery temperature is above operational range. | OPS-102 | |
| These conditions constitute the high temperature low power mode entry criteria. | |||
| OPS-304 | CPU Temp < 60ºC | ||
| AND | |||
| Battery Temp < 50ºC | The spacecraft shall exit low power mode when battery temperature is within operational range with margin. | OPS-101 | |
| These conditions constitute the high temperature low power mode exit criteria. |