Apologies for the delay on this. I've just been stuck with writer's block recently on this and I was spending some time on reworking out some of the outline on this and double checking through some stuff on this.
Hopefully I can try aiming to get back towards getting updates on this regularly, and not a month between updates on it. :/
IX
As both the United States and the Soviet Union undertook efforts on long duration spaceflight by space stations in 1973, the eyes and minds of many in both space programs were already planning for where to set onwards next; to go beyond low orbit and the moon towards Mars. In the wake of the initial celebrations of the Apollo lunar landings, it had been considered for a time among engineers from both space programs to continue on towards Mars, however the fiscal environment had made it apparent that it would never happen. Now in the wake of the Mariner Discovery, the desires to send an astronaut or cosmonaut to Mars had been supercharged, in the goal of seeking to arrive at the ruins first.
However, before the chance to land anyone on Mars could be performed, there was the need to
understand Mars much more, so as to allow those who arrived there to be able to survive in the significant different conditions from either Earth or the Moon. Many unknowns were still present for Mars, such as the full atmospheric composition, significantly more detailed orbital imagery, the Martian weather, soil composition, the magnetic field, the gravitational field, and many other factors. The determination to understand the gravitational field, was something that had come more-so for the Americans in the wake of the irregular nature of the Moon's gravitational field as determined by the Lunar Orbiters and subsatellites carried by Apollo 15 and 16.
To be able to solve the needed questions, would require launching robotic missions to Mars, but missions launched to Mars could not be launched willy-nilly. The nature of the universe dictated that the planets moved while orbiting the sun, meaning that Mars would not be in the same spot as it was on launch when the robotic mission would finish between Earth and Mars. Thus, one had to launch the mission based on where Mars
would be when it was supposed to arrive, rather than where it was now. The time when everything was in the 'right' configuration to head to where you were going were known as 'launch windows'. Launch windows governed everything in terms of rocket launches, no matter if one wanted to put a satellite into a desired orbit, to rendezvous with another object in orbit, or to go beyond the Earth to reach another destination. All of the planets had a consistently repeating launch window based off where the planets were in their orbits. If one wanted to head to Mars, the launch windows between Earth and Mars were 'open' every twenty-six months, when both planets would be in the right configuration to allow a mission to be sent out.
Following Mariner 9's discovery, four launch windows were available through the rest of the 1970s, 1973, 1975, 1977, and 1979. For both the United States and the Soviet Union, it represented four separate launch opportunities available to each state through the rest of the decade to send additional robotic missions towards Mars, to both explore it ahead of crewed missions
and to find out more about what exactly the ruins inside Steinbacher Crater were like.
The Soviet space program would make the first effort, launching a total of four Protons towards Mars throughout July 1973. The four Protons would make up a pair of orbiters (Mars 4 and 5) and a pair of landers (Mars 6 and 7), identical to those launched in the prior window of 1971. As a result of the higher demands imposed to reach Mars for 1973, the orbiters and landers had to be launched separately towards Mars, with the orbiters launching at the beginning of the window, in order to act as relays for the landers which would follow up with their launch at the end of the window. As the instrument suites and designs were identical to those sent in 1971, it would primarily improve upon the existing data that had already recovered, but also at the same time with flaws that were already present in the designs of the orbiters and landers.
In the start of the 1970s Sergey Afanasyev, the head of the Soviet rocket program, had placed his support behind a Mars Sample Return mission (entitled Mars 5NM) that could be launched in 1975 in order to act as the Soviet answer to the Viking program, which would have the Soviets
leapfrog the Americans by returning a sample of Mars back to Earth. In addition to the launch of a Sample Return mission, it was planned for a launch of a modified Lunokhod rover in the window prior to the launch of the Mars Sample Return in order to test technologies such as the aeroshell, in order to verify that they worked. Needless to say, a host of technical issues such as the concerns of a parachute failure on reentry causing a release of Martian soil samples across Earth and over whether or not systems on the spacecraft such as the avionics, could withstand the three-year trip in space, presented doubts that the project could be done. Georgy Babakin, the head of the Soviet planetary program, had opted to not proceed with the project citing the issues, but in the wake of his death, the project would be resurrected by Afanasyev, and following the discovery made at Steinbacher Crater, would be given a significant boost behind its sails.
Like before, numerous issues and concerns such as protection of the Earth biosphere from Martian bacteria and the lifetime of the avionics were significant issues that would need to be resolved before the mission could be flown. The delays from the cancellation of the project and its resurrection had already forced the precursor mission to launch in 1975 followed by the Mars Sample Return flight in 1977, but the list of issues that would need to be resolved before it could fly was still paramount. Numerous systems and components, ranging from the requirements of the usage of the Block SR to send the rover and Mars Sample Return mission to Mars, to the aeroshell needed to land the Mars Ascent Vehicle, and the three-year plus lifetime of the orbiter were all examples of what had to be worked on and completed before either of the missions could be flown.
At the same time as work was progressing on the Mars Sample Return plans, preparation and work was underway for the launch of an additional pair of orbiters and landers towards Mars in 1975 (in part from an expectation of a delay for the precursor mission to fly in 1977). Rather than flying copies of the previous missions, a new design would be utilized for the orbiters and landers considering the issues that had come about with Mars 2 and 3. It was planned that the new Mars orbiter bus would also be used for the Mars Sample Return mission and its precursor (rather than the Mars 2 and 3 buses as originally proposed), thus setting the kind of lifetime requirements as a baseline design for the proposed Mars 8/9 missions. The work on the dual orbiter-lander mission could not come into a better time, as news came that the Block SR stage would not be ready for flight until 1976, setting Mars 8 and 9 to be sent towards Mars to compete with Viking.
In comparison to the Soviet Union, the United States would be unable to launch a robotic mission to Mars in the 1973 window in part from the demands imposed by the Viking Program, and also over concerns in attempting to 'rush' in building a mission to reach Mars
[1]. The Viking Program, like Mariner Jupiter-Saturn, had come about from a much more expensive and broad program, canceled because of the mounting costs and reenvisioned as a program with a more focused goal. The mission for Viking, like Voyager
[2], was the search for evidence of life on Mars but unlike Voyager, it had been messaged that it would
not act as a precursor to a crewed Mars mission and also would have a significant reduction of costs in comparison (such as the launch vehicle using a the Titan IIIC with Centaur rather than the Saturn V as Voyager proposed).
At the core of the Viking Program, was the Gas Chromatograph-Mass Spectrometer and the biological suite. The Gas Chromatograph-Mass Spectrometer (GCMS) was the heart of the organic investigation. The GCMS was arguably one of the most complicated portions of the entire program, second to that of the biological suite, being designed to search for organic material in the Martian soil. The biological suite in comparison was intended for life detection. The biological suite was made up of four biological tests, pyrolytic release, labeled release, the gas-exchange experiment, and the light-scattering experiment. The four tests represented a significant spectrum of tests that were all designed to measure some portion of the metabolic process for Martian organisms.
The discovery made by Mariner 9 at Steinbacher Crater caused an ensuing impact on Viking, NASA's next mission to Mars. While there was an initial furor and debate on
if Viking still needed the biological tests considering the discovery, it was only apparent that life
had existed on Mars, but it did not answer the question of if life still existed on the planet or not. Viking was still NASA's next Martian program, but it was a program that was facing financial issues as a result of growing cost overruns because of the kind of leading edge technology required to be developed for the program, such as the entire chemical and biological suite for the landers. The cost overruns that Viking was dealing with would be alleviated to a degree by the general funding increase that NASA had received, as the drive towards Mars began to slowly accelerate.
While Viking's funding had been burgeoned and reduced the cost overrun issues, it could not help in other ways such as hardware issues that had to be dealt with. Emerging as one of the paramount hardware issues prior to the discovery, was the issue of the Viking lander biological suite. The biological suite as designed, was sized for the four experiments that had been planned from the start, but a mire of issues ranging from available power, to the increasing size and complexity of the experiments and the available size that was allocated for the entire biological suite was causing all kinds of issues. This was not including the issues that was being encountered by TRW (the contractor assigned to build the biological suite). After significant discussion, a decision had been finally reached to solve the issue; one of the four biological experiments would have to be deleted. The decision to eliminate one of the biological experiments was met with uproar by the biological team, arguing that the decision to eliminate one of the experiments was driven by the continued cost issues rather than issues such as weight or power
[3]. The experiment to be eliminated after significant discussion both on the engineering standpoint and biological standpoint would be chosen as the light-scattering experiment, which was deemed as the least damaging in terms of science lost and one of the more difficult to build. However, it was explicitly guaranteed that the light-scattering experiment would be flown in a follow-on Viking flight (after Viking 1 and 2).
Besides the lander, the other major portion of the Viking Program was the orbiter. One of the most crucial tasks of the Viking Orbiter was the kind of orbital imagery that would be performed prior to separation of the lander in order to verify site selection of where the scientists wanted the landers to land. A meeting of the ongoing cost overruns had been initiated for Viking in September 1971 with one of the options considered being the deletion of the Orbiter Imaging System, and it had become apparent at that time that the Viking Orbiter could be faced with a series of major cuts because of the mounting cost overruns from the Lander. The discovery made by Mariner 9 at Steinbacher Crater rapidly reversed those ideas, with the imaging system for the Orbiter being
vital for the needed follow-up imagery of what had been discovered, especially at the significantly improved resolution that could be expected from Viking over Mariner 9.
As work on Viking progressed, work on follow-on missions for the remainder of the 1970s was underway. A series of vital questions were still unanswered about Mars, ranging from the basic questions of what did the Martian atmosphere and surface consist of in terms of elemental composition to the more advanced such as how exactly has the Martian atmosphere come to be? Many of the questions that lay unanswered were vital for the designing of any kind of crewed Mars mission to explore what lay in Steinbacher Crater. The follow-on missions would be expected to be built off the knowledge garnered from Viking and the missions that followed it, with each window seeing missions that were
hoped to build off the knowledge of the previous one. The instruments for the missions however would lag behind the results discovered from the missions that preceded it, with the 1979 missions probably to be the first robotic missions that could build off of the knowledge and results gained from Viking (if not the 1981 missions).
The 1977 window would represent the first of the follow-on missions, and had been heavily contested between focusing more heavily on landers versus orbiters. Part of the issue between the two was the limited amount of capacity that was available by NASA's Deep Space Network for missions that could be flown. After significant discussion, from a scientific, engineering, and crewed mission planning standpoint, the decision was taken towards an orbital science outlook towards the planet. In addition to the purely operated orbiters that would be sent to Mars, the backup Mars Viking Orbiter and Lander would be sent in 1977 for additional research that could be performed. With the announcement of a new mission set for launch in 1977, Ames Research Center and the Jet Propulsion Laboratory (as the principal flight centers involved in designing spacecraft) set to work.
After the initial analysis of both designs, NASA announced that rather than flying of two either kind of orbiter (as had been normally done), they would be flying both of the orbiters. This in part was a result of both of the submitted designs representing a particular focus in their design and the both of them offering if launched together an explicitly 'complementary' approach towards the science gained rather than being explicitly oppositional. Ames had submitted a Pioneer mission
[4] which would work to study the upper atmosphere and ionosphere, the composition of elements on the Martian surface, and the interaction of the solar wind with Mars. JPL had submitted a modified Viking orbiter
[5] which would work on a geochemistry survey, measurement of the gravity field, and a detailed investigation of the Martian geology and climatology from orbit. As part of the announcement (from discussions held prior to the announcement), Viking 4 (as the JPL proposal) would be fully tasked towards mapping out the Martian surface in an even further detail ahead of any crewed missions, with Pioneer 12 (designated Pioneer J internally) to fly and study the Martian upper atmosphere, ionosphere, and magnetic field in addition to the interaction of the solar wind on the planet. Pioneer 12 would have the gamma ray spectrometer deleted (intended to map out the composition of elements on the Martian surface), in exchange for additional instruments to better study its assigned mission, something that the spinning spacecraft was well designed to determine.
With the missions for 1977 set, work began on outlining what the 1979 launch opportunity would see in terms of missions sent. A variety of options were being considered in the NASA Headquarters along with inside Ames Research Center, the Jet Propulsion Laboratory, and Langley Research Center (who was in charge of the Viking Program and the lander). Most of the proposals focused on landed science, ranging from making the Vikings mobile in some fashion to working on entirely new rovers as a mobile lab to a 'network' of penetrators across Mars. Each of the proposals was supported in some fashion by one of the flight centers, with Langley in favor of making the Viking landers mobile, to JPL wanting to design entirely new rovers as a mobile lab, to Ames wanting to do a network of penetrators for a long-duration gathering of info across Mars. For now, no real concrete decision had yet been reached by NASA in part from the effort being pushed into Viking and a series of other programs in progress.
The robotic programs of both the United States and the Soviet Union had a singular goal in the wake of the discovery, be able to find out enough information before the crewed program could be sent. A variety of plans were already underway for the rest of the 70s, to send a plethora of orbiters and landers to find out the most basic information about Mars that was not known about. For the 1980s, there was still a debate on what would follow up those missions prior to the arrival of astronauts and cosmonauts, with most of the ideas being thought around a Mars Sample Return in order to better understand the Martian soil and also over the concerns on how best to deal with Martian bacteria. But for both, the work being undertaken by the robotic program paled in comparison to the crewed program...
[1] Pioneer H was identified as being available to utilize, but the concerns of a loss on launch for either Pioneer F (launched as Pioneer 9) or Pioneer G (launched as Pioneer 10) in addition to the series of modifications required for Pioneer H as an orbiter was felt to be enough that Pioneer H could not be flown to Mars in the 1973 window.
[2] For reference sakes, this does not refer to the pair of Voyager probes launched in OTL, but rather the preceding Mars Voyager that had been worked on during the 60s.
[3] While IOTL, the removal of one of the experiments was because of cost, it's mentioned by NASA's Headquarters that there were also concerns driven by weight and power, while the biological team responded in that the weight issues weren't that serious, so this was something of a judgement call I had to determine when doing the research for this bit.
[4] This is based off the proposed Pioneer Aeronomy Geology mission, of which is available to read more on
here.
[5] This is based off the proposed Mars Polar Orbiter mission from the Space Science Board Summer Study held in 1974.