VELOX: a family of different experiments

NTU’s VELOX sequence includes small student-built spacecraft and more specialized experiments. VELOX-PII flew in 2013, followed by VELOX-I and VELOX-PIII in 2014. Their archive labels include VELOX-P2, VELOX-I and VELOX-PIII. These projects supported hands-on work across design, assembly, testing and operations, giving successive teams a platform for developing and trying new systems.

The family name does not imply that every member carries the same payload or answers the same question. A useful comparison asks what each experiment measures or enables, which partners supply its parts, and what evidence demonstrates its function. This approach makes the sequence more informative than a list of launch dates: learners can see why a team would change a design between flights.

VELOX-II, launched in December 2015, carried an NTU–Addvalue inter-satellite communications experiment. Instead of waiting only for direct contact with a local ground station, a low-orbit satellite can pass information through a higher relay. NTU’s milestone history reports the low-Earth-orbit to geostationary relay demonstration. The archive distinguishes VELOX-II from the separate VELOX-C1 spacecraft on the same launch.

Imagine a fictional sensor whose direct ground contact is thirty minutes away. A relay path that delivers the message after three minutes improves timeliness by twenty-seven minutes. This is an illustrative comparison, not a measured VELOX service guarantee. The relay still needs compatible radios, visibility, capacity and a working ground destination. Adding another spacecraft creates a new path; it does not make every communication dependency disappear.

One family, several questions

VELOX-CI used radio occultation — open definition: changes in navigation signals passing through Earth’s atmosphere can support estimates of atmospheric properties. Its research team assessed commercial receiver performance and limitations, including sampling constraints. Comparing a retrieved profile with independent atmospheric information requires attention to location and time; two measurements far apart may differ because they sampled different air, even when both instruments work.

VELOX-AM launched in July 2023 to test spacecraft parts made through additive manufacturing. Here the parts were manufactured before flight and exposed to the space environment; the name does not mean a printer produced the spacecraft in orbit. Taken together, relay communications, atmospheric sensing and materials testing show how one engineering family can support several scientific and practical objectives. Each objective needs its own measurements and criteria for success.