Access

Access analysis answers: when can my satellite see my ground station, and how well?

Running an access computation

Access computations take a propagated satellite and one or more ground stations, and return every visibility window in the scenario timeline.

For each pass you get:

• Start and end time (AOS/LOS — acquisition and loss of signal).
• Duration — typically a few minutes per pass in LEO.
• Maximum elevation — higher max elevation generally means better link quality and longer passes.

Illumination filtering

For satellite-to-ground-station access — with or without a sensor constraint — you can require a solar illumination condition to hold during the access. The condition gates the window itself: AOS/LOS boundaries land exactly on illumination transitions, so a pass that starts in daylight but ends after dusk is reported in two parts.

Setting	Description
Enable illumination filtering	Toggle on to require an illumination condition
Illuminated Object	Ground Station — sun elevation at the station site; Satellite — spacecraft eclipse state
Mode	Ground station: Daylight Only (sun above threshold) or Night Only (sun below threshold). Satellite: Sunlit Only or Eclipsed Only (inside the central body’s umbra)
Threshold (°)	Ground station only — sun elevation magnitude. e.g. 0° for the horizon, 18° for astronomical night

Typical uses:

• Optical ground stations — laser downlinks and optical tracking generally require a dark site, so set the station to Night Only with a threshold such as 18°.
• Visible imagers — require Daylight Only at the station.
• Power-aware passes — require the satellite to be Sunlit Only (or Eclipsed Only for thermal/shadowing studies).

Illumination filtering works for Earth and Moon accesses alike: a lunar satellite is checked for eclipse by the Moon, and a Moon ground station uses its own sun elevation. For AOI targets, illumination checks the region instead — see Area of Interest.

Target pointing

During access windows, you can override the satellite’s default nadir/ram attitude to point at a target on the ground. Two modes are available:

• Spotlight — the satellite fixates on a single ground target throughout the pass.
• StripScan — the satellite sweeps along a ground track direction.

Target pointing affects power generation (the sun angle on the body changes) and link budget (antenna boresight alignment).

Using the results

• Communication planning — schedule uplinks/downlinks per pass.
• Data budgets — combine pass durations with your downlink data rate to estimate daily downlink capacity.
• Station selection — compare candidate sites by total daily contact time before committing to a ground network provider.
• Power payloads — payloads can be configured to activate only during access windows. See Power.

Constellations

Access analysis works for constellations too: compute passes for every satellite against your station network to find aggregate contact time and gaps.

Next steps

• Ground Stations — define station locations and masks
• Power — access-activated payload duty cycles
• Link Budget — RF margin per access window