ch9-2

On Mars: Exploration of the Red Planet. 1958-1978



FINANCIAL PROBLEMS THREATEN ORBITAL IMAGING SYSTEM



[279] August to October 1970 was a busy time for the Viking project managers and the landing site working group. General discussions quickly gave way to deliberations over specific problems. One of those specifics was the orbiter visual-imaging subsystem, which had been identified as a candidate for elimination or modification to reduce costs substantially. The project stretch-out required paring costs, and Jim Martin and his colleagues sought ways to do so while still saving the orbiter and other key elements of the proposed mission. ⁵
The Science Steering Group had identified three alternative approaches to orbital imaging that would save dollars-the Viking camera system already proposed; a slight variation of the system in which the image motion-compensation device was eliminated at an estimated $1-million saving; or a modified Mariner 71 imaging system (using improved optics), at a possible saving of $8 million. ⁶ At the July 1970 Science Steering Group meeting, Viking project scientist Jerry Soffen had told his colleagues that the cost reduction exercise in progress made it necessary for them to decide which investigations or parts of investigations were the most important scientifically. Each science leader had to defend the costs and merits of his team's experiment and recommend ways to conserve money. When Mike Carr-orbiter imaging team leader and an astrogeologist from the U.S. Geological Survey, Menlo Park. California-had defended the orbiter television camera system, he had argued that the costs were as low as they could be. When asked if the Mariner 71 camera system could be used on Viking as well, he had said emphatically, no.
[280] Carr's orbiter imaging team reported in October that the orbital imaging from Viking would substantially enhance the scientific value of all the other experiments. ⁷ The imaging system would improve the probability of a safe landing, help define the environment in which the lander experiments would be performed, and permit comparisons of the landing site with other regions on Mars. The team was convinced that the proposed Viking camera system would yield superior pictures. "A modified 1971 camera would provide only minimal support for the Viking mission and would add only little to our knowledge of the planet. The Viking camera system outperforms the [Mariner] 71 camera in. . . .very fundamental ways.'' Mariner 71's camera was a slow-rate vidicon unit, requiring a cycle time of 42 seconds to capture a single image. Viking's fast vidicon worked in a tenth of that time. To get overlapping coverage with the Mariner 71 A-camera, it would have to look at a larger area, losing detail in its resolving power. Mariner 71's B-cameras had a resolution comparable to the Viking stem, but with a slow vidicon system it could not produce contiguous frames of coverage and would leave gaps between pictures. Viking's cameras would yield high-resolution and overlapping images, so the Viking team could get the photographic images they needed of the entire landing area in a single pass.
The fast vidicon camera system put other demands on the team, however. On the orbiter, the camera would require a fast, reliable tape recorder to store all the electronic bits into which the images had been coded. The telemetry system and ground-based recorders must be capable of handling the data flow, and the image-reconstruction and processing computers and related equipment would have to process that data as quickly as it was received. But Carr believed that this elaborate complex of machines and men was essential to Viking's success. "The Viking camera will always outperform the [Mariner] system by delivering more resolution per area [281] covered, by allowing greater flexibility in choice of filters and lighting conditions and making more effective use of a lower periapsis." ^*
These performance differences were important to site certification. "With only two landers judicious choice of landing sites is essential to ensure that they will result in maximum scientific return." According to Carr and his colleagues, orbital imaging would be the key to site selection by providing:
: (1) Numerical terrain data (crater statistics, slope frequency distributions, etc.) such that the landability of different sites can be compared and assessed.; (2) Distribution frequencies of features such as craters, ridges, block fields, that are potentially detrimental (or advantageous) to lander experiments.; (3) Absolute and relative elevation measurements as a supplement and check to radar and [infrared] data.; (4) Information on the geologic nature of the potential landing sites.; (5) Information on seasonally variable clouds, condensations, and surface albedo differences both locally and regionally around potential sites. ⁸

The orbital imaging team was sure that the difference in results from the Mariner 71 and the Viking systems would be striking. Mariner 71 would be unable to portray objects smaller than 1 kilometer in diameter, while resolution with the Viking system, judged to be about 45 meters, was "close to the limit from which data can be extrapolated to the scale of the lander [2-3 meters]." The orbiter imaging specialists contended that using a modified Mariner 71 system would render the imaging "virtually worthless for obtaining terrain statistics and the distribution of specific features at the scale of the lander or making useful elevation measurements." To make their point, they used 80-meter-and 1-kilometer-resolution photographs of the Apollo 14 landing site on the moon to illustrate how sensitive geological and topographical analyses were to this change. Most telling was the team's comment that the state of Martian imagery after Mariner 71 would be "roughly comparable to that of the Moon before any spaceflight program.
Besides searching for landing sites, the experts hoped the orbiter imaging system would return data on the activity of the Martian atmosphere, provide a much better understanding of the geological processes, and perhaps even yield clues to the existence or nonexistence of life. And there was the future to look to, they suggested. "The Viking landers will not be the last spacecraft to land on Mars. Others will surely follow and sites will have to be selected. Our whole lunar experience has been that the prime....







[Whole page 282] (Orbiter imaging team leader Michael Carr used Apollo 14 photos to explain the difference in imaging resolution between the cameras of Mariner Mars 71 and Viking orbiters. Resolution of about 80 meters for the top photo of the Apollo 14 landing site is slightly worse than the effective ground resolution of the Viking baseline camera. Chief justification for choosing the site was the presence of the Imbrium Basin ejecta, indicated by rough terrain in the west part of the photo. In the bottom photo, at a resolution of about 1 kilometer (comparable to that of the Mariner Mars 71 camera), the area looks bland and uninteresting the ejecta is not detectable. Details of the terrain are inadequate for assessing landing conditions and topographic and geologic content of the area.)

[283]....consideration in selecting any landing site is the availability of imagery." No judgment could be made about the relative merits of different sites for engineering or scientific purposes without adequate images. "In the past, a [lunar] site without imagery has been rejected immediately. There is little reason to believe that for Mars the decision making process is going to be significantly different." It was "imperative to collect as much imagery as possible to provide a decision making base for future mission."

Finally, the imaging team turned to political considerations.
: One of Viking's characteristics is its high-risk, high-gain mode of focusing on a search for life. Negative results on all the biologic experiments is not unlikely; the seismometer may never see a quake. To run a billion dollar mission and obtain largely negative results would be embarrassing politically for the projects as well as for NASA as an agency. Whether negative results reflect the lack of life, or the wrong kinds of experiments or the wrong landing locations might be difficult to see....
Thus, the high-imaging system may be considered as the "meat and potatoes" low-risk but guaranteed-significant-gain experiment in the mission.

It was excellent insurance against critics who might say that Viking had been too narrowly focused. The orbiter imaging team urged that the Mariner 7l camera system be dropped from further consideration. ⁹ The landing site working group recommended to the Science Steering Group that the Viking system be retained. and the steering group and NASA Headquarters concurred. ¹⁰
A year later, money problems recurred. On 19 September 1971, the Science Steering Group met in a special session where the science team leaders got the bad news. Despite all efforts to reduce costs in management and engineering phases, Jerry Soffen had to tell his colleagues they must reduce the overall science costs by $17 million to $22 million. Several methods were mentioned, but each team quickly put in writing reasons why its own experiment should be exempted from the reductions.
The 6-7 October meeting of the steering group at the California Institute of Technology concentrated solely on money matters. Three options for reducing costs were discussed at length. The first called for deleting some routine activities-holding fewer meetings, and the like; perhaps as much as $3 million could be saved here. By simplifying the gas chromatograph-mass spectrometer and the biology instrument, another $5 million or so might be cut. Reducing science activities on board the orbiter could save another million. Other parings and deletions brought the total potential savings to just over $22 million. The second option called for eliminating the gas chromatograph-mass spectrometer, which had a predicted $35-million price tag, but the Science Steering Group preferred not to act on this item until it had a better feel for the technical feasibility of building the instrument.
[284] Option 3 was the removal of the imaging system from the orbiter. As Hal Masursky recalled the scene, Soffen said, "We have a 17-22-million-dollar problem and the Orbiter Imaging System costs 25 million. Any suggestions?" Most of the steering group members were reluctant to recommend removing those cameras until they saw the Mariner 71 photographs. They would make that recommendation only if the Mariner images showed a bland, uninteresting surface. Mike Care and Hal Masursky believed the imaging system was necessary for site certification regardless of what data Mariner 71 produced. C. Barney Farmer, team leader for the Mars atmospheric water-vapor detection experiment, expressed his concern about the whole idea of using these meetings to effect cost reductions. He went on record indicating his reluctance to recommend the removal of any full investigation. The group postponed a decision on the third option until January-February 1972. Money had been, was, and would continue to be a problem. Still, it was only one part of the problem of searching for a landing site. ¹¹
^* Periapsis is the point in an elliptical orbit at which a spacecraft or satellite is closest to any body it is orbiting. Its opposite, or highest point, is the apoapsis. Specifically for Earth orbits, the terms are perigee and apogee; for the moon, perilune and apolune, and for the sun, perihelion and aphelion.