Danfe-II: run an experiment aboard someone else’s satellite

Danfe-II is the Nepalese payload contribution to PHI-1, the first flight of the Payload Hosting Initiative involving the Mohammed Bin Rashid Space Centre and UNOOSA. PHI-1 is the UAE host spacecraft; the APN experiment is one contribution aboard it. The program also provided a hosted opportunity to Bahrain. These partnerships let teams develop particular experiments while the host supplies shared spacecraft services.

UNOOSA’s 2025 annual report records the actual launch on 28 November 2025 aboard a Falcon 9. It identifies the Nepal experiment’s objective of testing PX4 Autopilot in orbit. Earlier APN design presentations also describe an integrated computing, power and radio approach and LoRa work. Those design objectives are useful context, but the launch report does not prove that every proposed function achieved its target performance.

A hosted experiment must agree with the spacecraft team about physical mounting, electrical supply, commands, telemetry and allowed operating times. The spacecraft bus — open definition is the collection of support systems that keeps the mission operating. Payload ownership does not mean ownership of the entire bus, and acceptance of a payload does not remove its integration responsibilities.

Consider an invented payload allocation of two watts. A processor uses 0.8 watts, its radio needs 1.6 watts while transmitting, and supporting electronics use 0.2 watts. Running all three together requires 2.6 watts, exceeding the allocation by 0.6 watts. The team could investigate scheduling, lower-power modes or a revised allocation with the host, but cannot simply assume that unused capacity elsewhere is available.

A payload must fit its agreed power allocation

A ground command may pass through the host’s receiver and software before reaching the experiment. Returned data follows another chain back to the researcher. To diagnose a missing result, preserve evidence at these boundaries: was the command received by the host, accepted by the payload, executed, stored and returned? A payload that ran correctly can still have an incomplete delivery record, while a received command does not establish successful execution.

Now imagine the host allows a ten-minute experiment window, but setup uses two minutes and safe shutdown one minute. Seven minutes remain for the actual experiment. The useful window is not the whole allocation. These numbers are teaching examples, not published PHI-1 operating limits. Hosted access reduces how much spacecraft infrastructure a team must build, while making interface agreements and shared-resource planning central parts of the engineering.