How ERMIS-3 held a laser link on target

Point, acquire, track

ERMIS-3, an 8U CubeSat, established an optical downlink with Greece's Holomondas Optical Ground Station (HolOGS-1). ESA says the demonstration tested precise pointing, acquisition and tracking (PAT).[1]

A narrow laser beam must be aimed at the ground receiver, acquired and kept aligned while the satellite crosses a short pass. Its narrow footprint makes precise tracking essential. Clouds can block the path and turbulence can degrade the signal. Higher-rate optical links could help move large Earth-observation files, but the trial does not establish all-weather service.[1]

Rates and limits

AUTh's 21 October release reports a current terminal capability of 1 Gbps. It says link-budget margin could support up to 10 Gbps; that upper figure is a projection, not a rate demonstrated in the reported test.[3]

ESA's programme account also describes up to 10 Gbps as link-budget headroom, not measured throughput. It reports that routine autonomous operation followed first contact within a week, reaching up to two scheduled links per day. That repeatable schedule goes beyond a single contact.[2]

First light is not dated

AUTh says the first contact took place on the first active pass; by the third pass, the systems were calibrated and running autonomously on a pre-scheduled plan. It gives no calendar date for first light.[3]