High level requirements for the Sapling spacecraft are described in the following. These top level requirements drive subsystem design for the rest of the spacecraft. Although some flow down from parent requirements or are grouped together, all are deemed important enough to either
| Requirement | Parameter | Description |
|---|---|---|
| SYS-101 | ≥ 1 beacon | The spacecraft shall communicate with the Durand Ground station. |
| Minimum viable mission success criteria. | The satellite shall provide data about its operations and its environment | |
| SYS-102 | Telemetry and spacecraft health | The satellite’s beacon packet shall provide data about its operations and its environment |
| Data provided in the beacon should inform spacecraft operators as to where Sapling is and how it is performing in those conditions. | The spacecraft shall take a photograph on command | |
| SYS-201 | 500-600 km | The spacecraft shall be compatible with a launch from a standard CubeSat deployer into a polar LEO orbit. |
| Polar LEO SSO allows for high revisit to the Stanford ground station and predictable thermal cycles. In addition, these are the most common orbital parameters for SmallSat rideshare launches. | >1 year | The mission design lifetime shall be at least 1 year of operations. |
| SYS-301 | ≥ 1 photograph | The mission shall produce a photograph of the Earth. |
| The mission goal of Sapling is to demonstrate Earth observation capabilities. This imaging requirement flows down to all payload subsystem requirements. | 1U | The spacecraft shall meet Cubesat Design Specification requirements |
| SYS-401 | Angular velocity < 10-3 deg / sec | The spacecraft shall be capable of coarse detumbling. |
| SYS-402 | Pointing accuracy < 20 deg from ground target | The spacecraft shall be capable of controlling its attitude. |
| These requirements flow down from SYS-201 because we suspect random tumbling inhibits downlinking capabilities. These requirements flow down to the ADCS subsystem. | ||
| SYS-501 | > 1 year operations | The mission design lifetime shall be at least 1 year of operations. |
| One year allows for a multitude of students to partake in spacecraft operations from the ground at Stanford. It also allows for testing of different ConOps and spacecraft commands. This operational lifetime requirement flows down to the power subsystem. | ||
| SYS-502 | < 5 years on orbit | The spacecraft shall deorbit safely after the end of mission operations without leaving any space debris. |
| Sapling may not contribute to the growing space debris crisis. Requirement ensures compliance with new FCC regulation. This requirement flows down to the orbital debris assessment requirements. | ||
| SYS-601 | 1U | The spacecraft shall meet Cubesat Design Specification requirements |
| Compliance with the CDS at a 1U form factor ensures that the spacecraft can be commissioned and deployed from a standard CubeSat deployer. | ||
| SYS-701 | The spacecraft shall be manufacturable in house at Stanford University. | |
| In house manufacturing advances our accessibility and student learning objectives. |