Satellite Constellation Planning
Definition
Satellite constellation planning designs groups of satellites that work together to deliver coverage, revisit, and capacity targets for imaging or communications. Key choices include orbit altitude, inclination, phasing, sensor type, downlink strategy, and redundancy. Models compute ground track geometry, access windows to targets, and contact times with ground stations. Trade studies balance swath width against resolution, single pass coverage against stereo or multi angle needs, and the cost of launch and operations against revisit performance. A good plan anticipates failures and maintenance maneuvers and defines a schedule for replenishment so service levels remain stable over years.
Application
Imaging companies design constellations to capture daily scenes of the whole Earth or to revisit cities many times per day. Disaster response agencies require rapid tasking to monitor fires and floods. Communications constellations plan continuous service with inter satellite links and global gateways. National programs plan mixed fleets that include wide swath monitors and high resolution tasking craft, along with thermal and radar sensors that work in all weather.
FAQ
How do altitude and swath trade against spatial resolution for an imaging constellation?
Higher altitude increases swath width and coverage per orbit but reduces ground sample distance. Lower altitude improves resolution but narrows swath and increases drag. Designers often mix buses, pairing wide coverage craft with narrow high detail craft to meet different tasks.
What is phasing and why does it matter for revisit time?
Phasing sets the relative positions of satellites in the same orbit so that ground tracks interleave efficiently. Proper phasing minimizes gaps and produces regular revisit intervals for key targets. Poor phasing can create clusters and long waits, even when the constellation size is large.
How do ground station networks and downlink capacity constrain planning?
Even with perfect coverage, data must reach users. Plan antenna visibility, contact duration, and bandwidth. Use onboard storage and compression, raise data through relay satellites, or expand ground stations to avoid backlogs. Legal overflight and spectrum rules also shape where and when downlinks can occur.
What reliability measures keep service stable when a satellite fails?
Maintain on orbit spares or drift satellites that can be phased in, design cross tasking between neighbors, and plan fuel margins for plane changes. Use health monitoring and predictive maintenance to anticipate issues. Document replenishment cadence so manufacturing and launch plans are ready before gaps appear.