BIRDS-X: compare satellite radio experiments fairly

BIRDS-X, also called Dragonfly, is a 2U CubeSat project led at Kyushu Institute of Technology. Its partners include Sri Lanka’s Arthur C. Clarke Institute for Modern Technologies and Amateur Radio Digital Communications. Building on the broader BIRDS educational program, it invited amateur-radio teams to develop payloads and ground terminals. This Dragonfly is an Earth-orbiting communications spacecraft, distinct from NASA’s mission of the same name to Titan.

JAXA’s dated deployment report confirms release from the Kibo module on 19 September 2025 under the J-CUBE framework. It lists a packet-radio competition, a low-cost UHF transceiver demonstration and volcanic-monitoring ground terminals among the objectives. Deployment establishes that the satellite entered its independent orbit. It does not, by itself, demonstrate that every experiment met its performance goals or that a monitoring service became continuously available.

The Automatic Packet Reporting System, or APRS, carries short digital messages. A digipeater — open definition receives a packet and retransmits it; a store-and-forward — open definition arrangement retains received data for a later delivery opportunity. Those are different operating modes. A sensor can collect a useful measurement while the intended receiving station is out of view, but the measurement only becomes available there after a successful later transmission.

For an invented timing example, a sensor takes a reading at 10:00, uploads it at 10:07 and the destination receives it at 10:19. The information is nineteen minutes old at delivery, even though only twelve minutes elapsed after upload. Preserve the measurement time as well as reception time. A late packet can still support research, but it cannot be treated as a live warning without considering the delay.

Measure the whole delivery path

Imagine terminal A attempts 100 packets and receives acknowledgments for 80, while terminal B attempts 200 and receives acknowledgments for 120. B delivers more packets, but A’s acknowledged fraction is 80 percent compared with B’s 60 percent. Neither total alone establishes the better receiver. The experiment must define whether it values overall throughput, delivery fraction, latency or some combination of those measures.

These are invented values, not published BIRDS-X results. A fair comparison also records visibility windows, antenna pointing, interference and the rules for identifying duplicate packets. Repeated copies of one message should not quietly become several unique measurements. BIRDS-X connects an international learning community to a real spacecraft experiment; a reproducible comparison makes that participation scientifically useful instead of merely counting contacts.