People have told me I’m a wonderful salesman, but it took all of my salesmanship while I was in Washington [to persuade NASA to fly the spin-scan camera].
—Verner Suomi to author, May 27, 1992
The spin-scan camera was a giant step. It gave you a view you didn’t have before.
—Robert White, former president of the National Academy of Engineering, to author, 1992.
n his long, narrow office at the University of Wisconsin, with awards hung on the walls (others are stuffed in drawers in the basement), Verner Suomi recalled the first spin-scan camera that he and Bob Parent proposed to NASA in the fall of 1964. “It was disgustingly simple. The stuff on the ground that you need to put the pictures together, that was not so simple.” The camera’s job was to continually monitor the weather over one portion of the earth’s surface.
The space-based elements of the idea were, indeed, conceptually straightforward: a spinning spacecraft in geostationary orbit, a telescope, a camera, and a data link with the earth. The practicality was a little more difficult. “But,” said Suomi, “one of the advantages was that we didn’t know what the problems were, so they didn’t hold us up.”
Suomi and Parent’s first proposal for a spin-scan camera, dated September 28,1964, was a hastily thrown together three and a half pages of text and two pages of very simple diagrams. Parent was the electronics expert. Their proposal was called “Initial Technical Proposal for a ‘Storm Patrol’
Meteorological Experiment on an ATS Spacecraft.” Like other meteorologists at the time, Suomi wanted to take advantage of the 22,300-mile-high geostationary orbit, in which a satellite stays in the same position, more or less, with respect to the earth and thus “sees” the weather moving underneath. Polar-orbiting satellites, by contrast, see successive snapshots of the weather in different places as they move through their orbit.
A geostationary orbit, however, is a long way away from the earth, so Suomi and Parent described a telescopic camera that would enlarge the distant image. Since only a small part of the earth would fall within the field of view, some method was needed of scanning in the east-west and north-south directions to build up an image of the earth’s surface. The satellite on which they hoped to mount the spin-scan camera would be spinning at a steady 100 rpm, and thus automatically would scan a line from east to west. After each revolution, the camera would shift its field of view slightly to build the full picture of the earth’s disc. Over the years, several electronic and mechanical methods of achieving movement in the north-south direction were explored.
Suomi and Parent thought that the image could be built over ten minutes from one thousand scan lines, giving a resolution at the subsatellite point of six nautical miles. In their second, ten-page proposal to NASA a year later, the camera, which was designed cooperatively with the Santa Barbara Research Facility of the Hughes Aircraft Company, had an image built from two thousand lines and thus an improved spatial resolution.
Today’s technological descendants of the first spin-scan camera scan sixteen thousand lines in thirty minutes. During severe storms they can build more frequent pictures of smaller regions. They observe in the infrared. Each radiometric reading is assigned a color, and a false-color image is created. From these images, meteorologists, infer wind speeds, which are particularly important for modeling atmospheric conditions in the tropics (within thirty degrees of latitude north and south of the equator), where the temperature differences are too small for satellite sounders to make distinctions.
Despite the greater spatial resolution of today’s satellites, Suomi, talking in 1992, was not happy about the thirty-minute time interval between photographs. In his opinion, the ideal interval is the ten minutes that he and Parent first proposed in 1964 because in that time very little change in the weather and very little detail of an evolving weather pattern is lost.
In that first proposal, Suomi wrote, “The object of the experiment is to continuously monitor the weather motions over a large fraction of the earths surface.” He and Parent envisaged a camera that would observe the earth between fifty degrees of latitude north and south, which would, of course, encompass the meteorologically all-important region of the tropics.
Suomi quoted results from his radiation balance experiments on Explorer VII and several of the TIROS satellites to make his case, writing that the amount of radiation reflected from the tropics was lower than expected, even though the total outgoing radiation from the earth was close to earlier estimates. Thus, more heat than previously thought was being transferred from tropical to polar regions.
The questions meteorologists needed to answer were, How was that heat transfer achieved, and how did it affect global circulation of the atmosphere? They had few observations with which to work because the tropics—the “boiler,” as Suomi wrote, of the giant atmospheric heat engine—which cover about half of the earth’s surface, are eighty percent ocean. The polar orbiting TIROS satellites did not help much. Those satellites spent only about fifteen minutes traversing the region as they headed north (similarly for the southward journey) in their orbit. There was a gap of twelve hours before the spacecraft was next above the same subsatellite point. In the tropics, where weather patterns develop and dissipate in far less than twelve hours, the result was that the TIROS satellites did not provide observations of the complete life cycle of a typical tropical storm. Instead, meteorologists inferred the progress of a “model” storm from observations of different storms in different places at different stages of their development.
Yet these storms, including hurricanes, are one of the mechanisms by which the “boiler” of the “atmospheric heat engine” redistributes heat around the earth. The rationale of the spin-scan camera was to provide data that would allow meteorologists to explore these mechanisms.
It took more than a decade for meteorologists to find effective ways of exploiting the spin-scan camera, but eventually inferences of wind speeds in the tropics improved atmospheric models.
Bob Ohckers, an electronics technician who joined Suomi’s group in 1967 from RCA, said that Suomi initially wanted to measure the winds from the displacement of clouds between successive images. “We’d get one image (an 8 by 8 transparency) in a frame and superimpose a second image taken twenty minutes later. First, we’d line up the geographical points in the two transparencies, completely ignoring the clouds. Next we’d shake the images in a frame until the clouds from the two images were superimposed on one another and the geographical features were displaced. You could tell when the clouds coincided because the light shining through from below was at it dimmest in those places. Then you would measure the x and у displacement of the clouds.” The method worked, but it was impractical, and the department’s software group came up with a better way of doing the same thing. When Suomi saw the results of the software, he dropped the mechanical approach without a backward glance.
Although meteorologists in the early 1960s were keen to observe the earth from geostationary orbit and plans existed on paper for a geostationary meteorology satellite, there was a problem. “No one had any idea,” recalled Suomi, “about how to get the blooming thing up there.”
Then Harold Rosen, Donald Williams, and Tom Hudspeth, of the Hughes Aircraft Company, came up with the engineering concepts that made attaining geostationary orbit both economically and technically feasible at an earlier date than anyone had thought possible. It was an advance that was to be a key factor in opening up the multi-billion-dollar business of civilian communication satellites in the mid 1960s, but a description of a NASA satellite based on the Hughes design also fired Suomi’s imagination. It was called, prosaically enough, the Application Technology Satellite-I. ATS-I was to carry an experimental communications payload with sufficient bandwidth to transmit a TV channel.
Suomi’s attention was caught by the simplified block diagram that accompanied the article describing ATS-i. It looked to him as though the satellite should be able to carry a small camera and that there would be sufficient bandwidth to carry its images back to Earth.
During July and August 1964, Suomi elaborated his ideas, and he and Parent hastily put them into their September proposal to NASA.2
Earlier in the year, Suomi had completed a brief stint as chief scientist of the Weather Bureau, working for Robert White (who later became president of the National Academy of Engineering, retiring in 1995). “Wouldn’t it be nice,” Suomi now asked White, “to beat the Russians into space with a camera viewing the weather from a geostationary satellite?” Seven years into the space age, many space scientists and engineers still felt they needed to regain the technological initiative from the Soviets. White’s practical response was to grease the bureaucratic wheels for Suomi, who, as with the International Geophysical Year, was making a belated entry into a satellite program.
NASA at first told Suomi that the spacecraft would not be stable enough for his camera. Suomi called Rosen at Hughes, who, incensed by the comment, made his own phone calls to NASA.
In the meantime, Suomi presented his and Parent’s ideas to government officials and industry representatives, including TRW and the Santa Barbara Research Center of the Hughes Aircraft Company. Both companies invested their own resources to investigate the concept. Several data processing issues had to be solved. For example, the camera was being designed to have a precise geometry, and the geometry of the resulting image had to be preserved after processing. Second, from geostationary orbit, the Earth occupied only about 16 degrees of the camera’s 360 degree field of view (because it was rotating). So the camera would be recording images of the earth for only about a twentieth of each revolution, and the signal would take up twenty times more bandwidth than was needed to relay the image data. There were questions, too, about the impact of camera distortion and about nutations of the spin axis (precession).
NASA backed the proposal in time for the camera to fly on the ATS-1 spacecraft. Suomi kept the technical authority for the project at the University ofWisconsin but subcontracted the physical construction and final engineering to the Santa Barbara Research Facility.
Some years later, Hughes filed a patent on the spin-scan camera, but Suomi opposed them, supporting NASA’s claim to the patent because it was the agency that had funded his work and because Suomi believed that the validity of the Hughes patent claim rested on his ideas. NASA, which would be less fortunate during a later patent dispute with Hughes about crucial elements of the Williams, Rosen, Hudspeth satellite design, won the dispute. Nevertheless, as Suomi said some years later, Hughes engineers made important contributions to the development of the camera, and, he added, . Hughes built the camera, so in a manner of speaking, they reduced the idea to practice.”
Suomi almost missed the launch of ATS-1. He had forgotten to do the paperwork for his security clearance, but a colleague interceded for him. Suomi said his most exciting professional moment came when the first image of Earth’s disk ever taken from space appeared on an oscilloscope. The aim of the spin-scan camera had been to have weather imagery available to meteorologists in real time. That did not happen immediately. The first printed images from the spin-scan camera on ATS – і were ready four or five days after the launch. Suomi was scheduled to give a lecture at the American Meteorological Society. He said, “I had a whole bunch of negatives, and I tried to line these up with one another. I put a pin through, and I made a “movie.” I gave my talk and ran the movie. They thought it was wonderful to see the clouds moving.”
They had, in fact, seen the first ever animated picture of the earth’s weather—the primitive precursor to the pictures that appear today on television weather forecasts. There was still a long way to go before the technology would be regarded as mature, but one of the two most significant classes of instrument (the other was the sounder) that would facilitate that process was aloft. And it was mounted on a satellite that was the technological kin of Early Bird, the world’s first commercial communication satellite