Hermes: test a communications technology with real users

Hermes was the Communications Technology Satellite, or CTS, developed through a Canada–United States cooperation program and launched in January 1976. Canada’s Department of Communications and NASA divided spacecraft, launch, amplifier and test responsibilities. The program investigated high-power communications at 12 and 14 gigahertz and the use of smaller ground terminals. This satellite is distinct from unrelated spaceplanes, rockets and later missions also named Hermes.

The engineering objectives connected several systems. An amplifier required electrical power, solar arrays supplied that power, and attitude control kept the communications payload pointed appropriately. Improving one component did not remove the need to operate the others together. The experiment therefore concerned an integrated communications capability, including what could be installed and used on Earth, rather than a transmitter specification in isolation.

NASA Lewis developed portable and transportable earth terminals for Hermes users. The historical report describes television and voice applications in education, health care, government and other activities. A terminal included receiving and transmitting equipment along with facilities needed to use the connection. Moving suitable equipment to a user’s location let the project explore applications beyond a permanent major ground station.

A useful demonstration must define what worked. Receiving a clear lesson broadcast establishes one capability; allowing students to ask questions requires a functioning return channel as well. The complete evaluation also includes setup, operator training and the conditions under which the link was tested. Success with one configuration does not establish that every possible terminal, location and operating condition will perform identically.

A fictional interactive-service trial

Imagine a fictional trial with 20 scheduled interactive sessions. Eighteen complete both directions successfully and two experience a return-link problem. The observed complete-session rate is 90 percent. Reporting only that all 20 locations received video would miss the failed interactive requirement. Neither result is a universal reliability estimate; the sample and tested conditions limit what can be concluded.

The CTS project’s retrospective records both technical work and user experiments. Lessons from demonstrations can inform later services, but operational rollout requires additional decisions about equipment, staffing, costs and maintenance. Hermes helped explore what communications satellites could enable for smaller ground installations. Its history encourages a practical question: which demonstrated capability addresses the users’ need, and what further evidence is required before promising it as a routine service?