RWASAT-1: follow a measurement from the ground

RWASAT-1 was developed through cooperation between Rwandan institutions and the University of Tokyo. JAXA records its deployment from the International Space Station’s Kibo module on 20 November 2019. The 3U CubeSat combined a training purpose with a receiver for collecting information from ground sensors. The project therefore linked spacecraft engineering with a practical question: how can a measurement made in a remote location reach somebody who needs it?

A sensor and a satellite do different jobs. A ground instrument measures conditions at its own location. The satellite receives a message containing that measurement; receiving the message does not mean the spacecraft itself measured the same quantity from orbit. Keeping these roles clear helps a reader interpret a mission description without confusing a radio relay with an imaging instrument.

Consider an invented field experiment. A sensor measures water level at 09:00, its message reaches a passing satellite at 09:20, and the ground team receives the relayed record at 10:05. The measurement is 65 minutes old when it arrives. The 20-minute wait for collection and the following 45 minutes are separate parts of the delivery delay. These figures illustrate the process; they are not RWASAT-1 performance measurements.

If the message contains only the reception time, a map could incorrectly present an old observation as a fresh one. Preserve the observation timestamp, sensor identifier, location, units and a sequence number. Reception time is also useful, but answers a different question. Together these fields help detect late messages, duplicate copies and gaps in a sensor’s record.

A measurement has more than one timestamp

For a slowly changing water reservoir, a delayed reading may still be useful. For a rapidly rising stream, the same delay may be too long for an alert. Decide what freshness the user needs before calling a delivery successful. A radio contact can work correctly while the resulting information arrives too late for a particular decision. The application requirement determines whether that matters.

Capacity building also reaches beyond the spacecraft. Teams need to test field instruments, recognize malformed messages, schedule contacts and explain uncertainty to users. A successful deployment establishes that a satellite was released; it does not demonstrate every proposed service. RWASAT-1 offers a concrete way to connect national engineering experience with the full path from measurement to interpretation.