An illustration of the original Intelsat IVA design. Note the four mesh antennas. (credit: Hughes)

Big comm, little mysteries

by Dwayne A. Day
Monday, December 5, 2011

A picture may be worth a thousand words, but sometimes a picture can be damned confusing.

While looking at the back cover of the June 1973 issue of Space World magazine, I noticed an artist impression of the Hughes Intelsat IVA communications satellite. The Intelsat IVA (i.e. “4A”) was a follow-on to the successful Intelsat IV satellites first launched in 1971. The first Intelsat IVA was launched in September 1975, and it substantially improved on its predecessor, dramatically increasing the number of television and telephone circuits that could be transmitted across the oceans.

But this artist impression did not look like the actual spacecraft that was launched. It featured four circular wire mesh antennas, two more than the Intelsat IV. The Intelsat IVA as launched actually had two large and one smaller squared wire mesh antennas.

In fact, Aviation Week had already printed another image that conflicted with both of these. The November 20, 1972 issue contained a small photo of a model of the Intelsat IVA satellite. This model featured four solid (not wire mesh) dish antennas.

A model of Intelsat IVA. Unlike the original illustration, it has four solid (not mesh) antennas. (credit: Hughes)

It is hard to write corporate history because corporations don’t open their archives except in rare situations. The evolution of Hughes’s highly successful satellite business is therefore mostly shrouded in corporate—and national security—secrecy. The evolution of specific satellite designs is equally problematic. Hughes engineers published several articles about the Intelsat IVA soon after the satellite type entered service, but none of them mentioned how the design evolved before it was finalized, or who deserves credit for different aspects of the design. That’s why the artwork and the model may tell a story.

Artist impressions, even physical models, don’t necessarily reflect the actual blueprints that a company’s engineers are drafting. But it seems likely that the Hughes’s artists who built the Intelsat IVA model, and later drew the Intelsat IVA illustration, were communicating with some of the engineers who were actually designing the new satellite. The evolving designs imply that at some point in the development, somebody—or several somebodies—determined that there was a better way of increasing the comsat’s communications capabilities than simply adding more dishes. At some point after that they went from solid dishes to wire mesh dishes. But at some point after that, they reduced the number of dishes from four to three. We can guess that these decisions resulted from the need to reduce weight as well as improvements in antenna design. But we’re guessing, we’re not confirming.

A photo of an Intelsat IVA satellite, showing two large and one smaller, rectangular mesh antennas. (credit: Hughes)

What this example also demonstrates is that before a space mission is launched, the public primarily sees artwork of the spacecraft. After the mission is launched, they see photographs of what actually got built, and the artwork—especially if it is inaccurate—is usually never published again. In the case of the Intelsat IVA, the artwork revealed an unknown aspect of the satellite’s history. Probably worth more than 1,000 words.

Admittedly, the Intelsat comsats are not the sexiest spacecraft. But in addition to their role in the development of the commercial communications industry, there are some indications that they are closely related to several types of intelligence satellites also built by Hughes. Hughes built the JUMPSEAT signals intelligence satellites, first launched in 1971, and the Satellite Data System relay satellites, first launched in 1975. Considering that Hughes was producing a lot of spinning comsats at this time, it’s reasonable to assume that they are all related. Pictures of either of those would be worth way more than 1,000 words.

Dwayne Day is interested in hearing from anybody who can shed some light on the development of the Intelsat IV and Intelsat IVA satellites. He can be reached at zirconic1@cox.net.

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