Good afternoon everyone! It's that time once again, and today's post should be somewhat timely given the topic of discussion that's popped up overnight, as Workable Goblin takes us on a journey to the Martian moons with the American-Russian collaboration mission Phobos Together.
Eyes Turned Skyward, Part III: Post #17
As the Soviet Union crumbled during 1990 and 1991, the Ares Program, part of Project Constellation, was planning a series of missions to Mars during the late 1990s and early 2000s to prove many of the technologies needed for a human flight, as well as return scientific data relevant to the success of a future human mission. With the increasingly open attitude of the Soviets, and eventually the Russians to international collaboration in space exploration, and a desire by the Bush Administration to diplomatically engage their former opponents, Ares Program management began to consider whether a joint venture with the Soviet Mars program might be usefully incorporated into their plans. The missions to Phobos proposed by the Russians for 1994 and 1998 seemed particularly ripe for outside involvement, particularly the sample return mission proposed for the latter opportunity. Although a mission to Phobos was obviously a diversion from Mars itself, it could still prove fruitful in the technology development role, proving a number of technologies and techniques vital for other, more directly important missions, such as autonomous Mars orbital rendezvous, automated Earth return, and long term operations in cis-Martian space. Moreover, any American assets included in the mission plan could investigate Mars as well as Phobos while in Martian orbit, and it would be possible to carry out other missions in parallel, so that overall Ares Program goals could be achieved while also taking advantage of a historic opportunity for cooperation between two formerly hostile nations. Thus, beginning in late 1991, representatives of Lavochkin, the Russian Academy of Sciences, Johnson Space Center, the Jet Propulsion Laboratory, and the National Academy of Sciences began a series of meetings intended to explore the possibilities of cooperation between the United States and Russia on one or more planetary exploration missions. In the course of these meetings, proposals were mooted for missions to Venus using the nearly-complete DZhVs-14 hardware, helioscience missions similar to the planned Lomonosov missions, a set of Pluto flybys to follow up Voyager 2, missions to the asteroids, and more, but the subject repeatedly returned to Mars and its nearest moon.
The tentative mission design that developed over the course of these meetings included significant components from both the United States and Russia. The latter would contribute the launch vehicle, a Vulkan-Blok R, and the Fobos-Grunt (“Phobos soil”) lander/sample-return collection vehicle, while the former would contribute a Mars orbiter/return vehicle responsible for collecting the sample container and returning it to Earth and a Phobos rover to be landed by Fobos-Grunt to explore the surface of the moon more thoroughly than possible by the stationary lander. In parallel, a Delta 4000 would deliver a pair of stationary landers to Mars to explore each of the poles of Mars for a few months. Although this latter was a purely NASA element with no significant contribution by or involvement in the Russian side of the mission, it was nevertheless considered by NASA to be a significant element of the overall Mars/Phobos ‘98 mission concept, kicking off the intense series of missions envisioned by the Ares Program to lay the groundwork for an eventual human flight.
Gore’s victory in the 1992 election disrupted but did not destroy this tentative program of cooperation. Although Gore was hostile to the massive scope of Project Constellation (and successful in terminating the Ares Program), the nascent Fobos Together mission had the advantage of being a positive diplomatic contact with a new Russia no one was quite sure how to handle yet, and one which could theoretically be leveraged to assist in the significant policy goal of ensuring that Russian technology, especially space and missile technology, did not proliferate and threaten American national security. As such, the mission was reorganized under a different aegis soon after the end of the Ares Program, with a new focus on cooperation with Russia. The mission quickly lost its costly Mars-centered elements, becoming a pure Phobos sample return. Besides eliminating reminders of the old regime, this saved the hundreds of millions of dollars which would have been needed for the lander design and construction, the launch vehicle, and operating the mission itself. The beginning of the Comets and Asteroids Pioneer Program in 1994 further solidified Fobos Together’s place in the American planetary mission canon, justifying it as a valuable precursor mission for the planned capstone comet and asteroid sample return flights. Given the similarity of Phobos’ surface environment and gravity to many asteroids, experience in building systems able to function there would be directly translatable to CAPP missions, while the orbiter’s planned electric propulsion system, more technologically advanced than Piazzi’s or Kirchhoff’s, could be reused for other missions, including those planned for CAPP.
In the meantime, the initially positive relations between the Russian and American elements of the project, were quickly souring, as cultural misunderstandings and technical problems piled up. To the Americans, the Russians seemed sloppy, careless, and unwilling or unable to address serious issues in their spacecraft, with multiple potentially mission-ending problems found during American inspections of spacecraft prototype components. For their part, the Russians viewed the Americans as arrogant and imperious, dictating changes and modifications without consulting their Russian counterparts and without due regard for Russian conditions. Matters came to a head after the disastrous launch of “Grand Tour” in 1996; only minutes after successfully completing its interplanetary injection burn, the spacecraft switched to safe mode, turned its solar arrays away from the Sun and refused to respond to ground commands, a state it remained in until its batteries expired hours later. The immediate effect on Fobos Together was dramatic, as the NASA contingent insisted on a thorough examination and review of all components, supervised by themselves, and far more stringent quality control procedures, also managed by the Americans, as they had lost all confidence in the managerial ability of their Russian colleagues. While the Russians were naturally outraged by these demands, the fact that NASA was in effect providing all of the funding for the mission forced them to accede to the American requests. The demand drove a wedge into the cracks already opening between the two parties, opening the small gaps into a yawning and irreparable divide, permanently damaging relations. Such a thorough review also forced a slip in the launch date from 1998 to 2001, although difficulties with the Russian manufacturers had been making such a slip look more and more likely in any case. With American oversight firmly established, the relationship between Russian and American project members became less tense, if still unpleasant in general, and progress on the project became steady if slow. As the new millenium dawned, Fobos Together was clearly on course to launch by the new target date, but the original purpose of the mission was being drowned in a pool of bad blood.
Nevertheless, it was on course, and in an environment where it had faded into the background as more photogenic opportunities for collaboration and greater concerns over Russian-American friction had arisen this was a powerful asset. Marching forwards, not always steadily, it managed to largely escape critical scrutiny, whether by Congress or the Federal Assembly, maintaining a low but funded profile. In late 2000, a few months after Fobos-Grunt had left the plant near Moscow for Baikonur, the American elements of the spacecraft arrived, ready for final integration into the launch stack. By April of the next year, they were ready, and apparently so was Earth, for a patch of brilliantly clear, cloud-free, cool, and still weather opened only a few days before the beginning of the Mars launch window. In a low-key triumph, overshadowed by the successes of Project Artemis, preparation and countdown proceeded problem-free, and the spacecraft were injected onto a trans-Mars trajectory on the first attempt. It was a far cry from the conditions that had prevailed a decade earlier.
Once it was confirmed that the spacecraft were on track to reach Mars, they came to life under the guidance of ground controllers, activating the ion drive to assist in the process of reaching Martian orbit, swinging the orbiter’s solar panels to face the Sun, and confirming the good health of the sleeping lander and rover. With all systems checking out, Fobos Together began the long journey to Mars. As usual for spacecraft cruising between the planets, the orbiter’s small suite of scientific instruments was turned towards observations of the Sun and interplanetary space, serving as much as a source of engineering data as scientific information. Just over six months after launch, in late October of 2001, the stack quietly entered a highly elliptical Martian orbit, gradually braked into orbit by its ion engines. Over the coming months, the orbiter slowly lowered itself towards Phobos’ low orbit, gradually circularizing its orbit just under 6,000 kilometers above the Martian surface, allowing it to slowly lap the moon in its tread around Mars. As it approached, it imaged the surface of the little moon, collecting compositional data from a few spectroscopes and building on the data returned by Mars 12 and 13 about Phobos. Eventually, it came to a halt just a few kilometers away from the moon’s surface, parking itself at the Lagrange point of Phobos and Mars and releasing the Russian lander to approach the Phobos surface. Gradually, over the course of a day, Fobos-Grunt drifted towards the tiny moon on near-invisible attitude control jets. Without any of the fire and fury of a landing on Mars or the Moon, it finally touched down near the middle of 2002, more than six months after entering Mars orbit.
In Russia, it was a minor media sensation. While a Russian had landed on the Moon in 1999, on Artemis 4, it had been three years, and this time instead of being a mere passenger on another country’s mission (ignoring for the moment the fact that Russian components had been critical for that mission’s success) this time Russia was in the driver’s seat. The mission concept had been a Russian idea, the launch had been on a Russian vehicle, and the lander had been designed, built, and tested in Russia. Never mind that the rover it was carrying was American, that it was carrying instruments from Germany, France, and Italy in addition to its Russian ones, that American quality control had been crucial for ensuring that it actually worked, or that it was only part of the mission, and depended on the NASA orbiter for success; for the moment, all that mattered was that the lander itself was Russian.
Outside of Russia, and lacking the patriotic and nationalistic overtones inspired there, coverage of the landing was more muted. In Japan, with no connection to the mission, it was virtually ignored in favor of focusing on Japan's Moon-bound Japanese astronauts of Artemis 6 and 7. In the United States and elsewhere it earned a little more coverage, due to diminishing public interest in the Artemis missions as they came and went, but still not much more than a brief mention on the nightly news, mostly because of the dramatic imagery returned from the surface of the little moon and the looming disc of Mars overhead, covering a vast portion of the celestial sphere, totally unlike anything seen on Earth, or even the Moon.
Nevertheless, the probe soldiered on, unaware of and unconcerned by the lack of press coverage. After a day of systems check-out, it was ready to take the next step: deploying the rover. A curious creation of JPL, the so-called “rover” resembled its predecessors on Mars or the Moon only in that it was intended to travel across the surface of Phobos to provide a more varied scientific picture of the body, otherwise having almost nothing in common with those spacecraft. The key difference was gravity, or rather, because of its small size and low density, Phobos’ virtual lack thereof. With no gravity, there would be virtually no frictional force holding wheels to the surface, turning it into the deceptively rocky, dusty equivalent of an ice sheet. Conventional wheels would be unable to gain traction and would struggle to maintain all but the most modest speeds without spinning out or launching the rover into space.
Facing this seeming disadvantage, JPL had turned it around and spun it into the centerpiece of their rover’s movement strategy. Rather than fight the low gravity, the rover, named Sojourner after the abolitionist Sojourner Truth and the fact that it was, as the name said, a wandering traveler, would instead exploit it, using Phobos’ extremely low escape velocity to ballistically travel all over the surface. This could be done using a simple set of springs, compressed using solar power during Phobos’ short days, then released to propel the vehicle across the surface. A set of hydrazine thrusters could be used to adjust the precise trajectory, and an additional set of springs on the sides of the rover, less powerful than the main propulsion ones, allowed it to pop back up into the correct orientation no matter how it landed. All in all, it was a clever design, and one very suited to moving over Phobos’ surface.
As Sojourner left its storage position on Fobos-Grunt to begin its slow circumnavigation of Phobos, the main lander turned towards its primary mission--extracting samples of the moon for analysis on Earth. Its sampling arms unfolded themselves from their stowed positions and began to delicately poke at the surrounding regolith and rocks, trying to determine which of several end tools that had been packed would be most suited for sampling the surface. Despite Mars 12’s landing on the moon more than a decade earlier, the physical properties of Phobos’ surface were still relatively unknown. Because of this, it had been deemed unsafe to include just one version of the equipment needed to recover regolith and rock samples from the surface; if the design assumptions that tool had been developed against were untrue, the entire billion-dollar mission would be an almost complete failure. In the event, the original Russian design proved to be the most suited for the conditions on Phobos’ surface, and after a week of work samples of loose regolith and entire small rocks from all around the lander were neatly tucked away in the sample capsule atop the lander body.
At the same time, the lander was working on obtaining samples from another area: directly underneath. It had long been known that Phobos has an exceptionally low density for being an ostensibly rocky body, just 1.8 grams per cubic centimeter; indeed, in 1958, prompted by early observations and estimates which seemed to indicate an even lower density, the Russian astrophysicist Iosif Shklovsky (probably best known to most readers for his influence on Carl Sagan) proposed that Phobos was actually an enormous hollow artificial body of some sort. While this particular theory fell afoul of better observations, it contained a kernel of truth, as those same observations showed that Phobos must have a considerable amount of so-called “void space,” where the chance accumulation of mutually gravitating fragments had left small gaps and cracks of empty vacuum within the body. The remaining question was what, exactly, the moon was made out of, and it was on this question, and this one alone, that the whole Fobos Together mission had begun in the first place, for there were two facts about the moon which seemed to point in entirely contradictory directions.
First, it was clear from even the most cursory observations that Phobos had an extremely small albedo, that is that it was extremely black--nearly as dark as fresh asphalt. By itself, this would not be so strange, as many C-type objects, commonly known as carbonaceous chondrites, are also quite dark in color, and it is plausible that during the early formation of the solar system such material could have coalesced to form a moon of Mars, whether around the planet itself or elsewhere in prelude to a later capture. Where the problem arose, however, was that spectroscopic observations of Phobos’ surface indicated that it was as dry as the Moon, with almost no water at all. Carbonaceous chondrites, however, contain a great deal of water, leading to a puzzling contradiction with the albedo data, as well as other lines of investigation pointing towards a more carbonaceous chondritic composition. Two theories had arisen to try to resolve this complication. The first proposed that the outer surface of the moon had simply been altered by billions of years of impacts, with whatever water had been locked into hydrated minerals having been driven out by shock-heating, leaving a dry, powdery regolith crust over a wetter interior, while the second argued that the moon was actually composed out of more typically chondritic materials and had had its appearance changed by prolonged bombardment to the dark color observed. Both of these theories had external support; it took little imagination to see how impacts could gradually drive off water trapped in hydrated minerals from surface material, while the existence of so-called “black chondrites,” transformed in exactly the same way proposed in the second theory, lent it considerable support. However, in both cases the essential information needed to differentiate between them was locked away under the moon’s surface.
Therefore, from the very beginning of the mission it was considered essential to include a tool capable of digging much deeper under Phobos’ surface than the simple grab tools and sifters of the primary sample collection arms, a core sampler. While space and mass constraints prevented inclusion of a tool able to dig really deep into the moon, it was hoped that even a shallow core could reveal possible gradients in volatile content that could point to the existence of more volatile-rich interior material. Knowledge of whether or not it did would be valuable to the Ares Program; if Phobos was as water-rich on the inside as the first theory predicted, it would have a reserve of potentially billions of tons of extractable water, enough to easily supply an orbital base and decades, if not centuries, of missions to and from the Red Planet. While NASA was not undertaking an active Mars program, nor expecting to in the next few decades, the purpose of the Ares program was still to provide the knowledge needed to plan any such missions, and the presence or absence of such a massive and easily accessible water reserve was certainly something that would be important to determine before any long-term plans were drawn up. When combined with the major technical demonstrations included in the mission, Fobos Together was perhaps the most important overall probe of the Ares Program.
In any case, despite early problems with the drill motor, Fobos-Grunt spent several weeks digging into Fobos’ surface, obtaining partial samples from up to three meters under the surface and a complete core of the first ten centimeters of regolith (the longest section that could be fit within the sample capsule). With both core and surface samples recovered, only one last step needed to be taken by the lander for its part of the mission, at least, to be a complete success: launch. Fortunately, in the extremely low gravitational pull of Phobos, this was not much of a challenge; with an escape velocity of just 12 meters per second, and a planned rendezvous near the Mars-Phobos L1 point (requiring even less delta-V), a set of springs very much like the ones implanted on Sojourner were more than sufficient to launch the capsule towards the orbiter, waiting overhead, in late August of 2002. Within minutes the orbiter had locked on to the sample capsule, and on gentle breaths of ion breeze it quickly coaxed the capsule into its final storage position. As soon as the two had connected, the orbiter turned its attention to the long journey home, boosting away from Phobos on its ion drive.
Even as the orbiter departed, though, the surface elements were still active and returning data to Earth. Sojourner continued to relay data from all over the surface through Fobos-Grunt, while the lander’s own suite of instruments silently collected data from around the landing site, even performing some in-situ analyses of collected material while the bulk returned home. After all, this departure had been planned from the start, and it took little effort to make Fobos-Grunt capable of transmitting directly to and from Earth, not just to the orbiter. Indeed, disregarding commanded shutdowns from Earth, the only threats to their continued operation was themselves. Sojourner was the first to cease functioning, running out of vital hydrazine in early 2003, after just over six months of operation. With no way to trim its trajectory, it would have been unable to make a precision return to Fobos-Grunt for updated commands or to relay any recorded detail. Emergency instructions for just such a case had been included in the rover’s memory, however, and it is assumed that it performed a nominal shutdown in line with the operations plan uploaded a few weeks earlier. If so, the rover’s hardware is likely, given the vacuum and quiet of the moon’s surface, relatively intact; the electronics systems may have been damaged by bombardment by cosmic rays and solar radiation, but the mechanical systems should still be operational if a future mission travels to the moon.
With no consumables and no need to move, Fobos-Grunt proved much more durable. The Russian lander soldiered on long after Sojourner had given up the ghost, relaying measurements to its Russian controllers. As one of the only active Russian planetary spacecraft, and still scientifically productive, concerns of prestige and image demanded that the Russian government continue to provide the relatively paltry sum needed for continued operation. Indeed, Fobos-Grunt would have continued its mission indefinitely had a relay in the power control system not failed in mid 2008, preventing the batteries that powered the lander through the night from charging during the Phobos day. With the moon’s day-night cycle only eight hours long, within a day the lander had permanently expired from loss of power.
While Fobos-Grunt and Sojourner continued their missions, the orbiter was breaking out of Martian orbit on the journey home. Powered by its ion engines, it retraced the trip it had taken just two years earlier to reach Mars through the rest of the year and into the next. Just two weeks before it returned to Earth, the reentry capsule into which the sample capsule had been tightly packed after its recovery separated, headed directly for the tiny blue crescent ahead. Its mission complete, the orbiter began nudging itself away from its home planet, diverting itself to pass by into a solar orbit where it would continue to operate as an interplanetary monitoring station and testbed, operating its ion engines until they ran out of propellant or failed.
Meanwhile, the return capsule plunged into the atmosphere above the Sary Shagan test range in Kazakhstan, less than a thousand miles from where it had departed Earth. An anti-ballistic missile testing range, Sary Shagan was well-equipped to track and follow the trajectory of objects reentering the Earth’s atmosphere, and almost as soon as it entered it was being tracked by the site’s giant radars, a peaceful application of the technology they represented. While the capsule was tracked to its landing just outside and to the northeast of the site’s boundaries, unseasonably poor weather and nighttime conditions prevented immediate recovery. Instead, at dawn the next morning, when the weather front had passed and visibility had returned to normal, a squadron of helicopters departed for the predicted touchdown location. With the aid of the onboard radio beacon, it took less than an hour for the recovery crews to find the reentry vehicle, which was immediately transported to the facility’s airstrip, where a long-range transport was waiting. Sealed in a special contained pressurized with pure nitrogen to prevent contamination by ambient air, the whole return capsule was immediately transported to Moscow, where it was carefully disassembled by a Russian team at the Vernadsky Institute of Geochemistry and Analytical Chemistry, or GEOKhI, the central Russian institute for the storage and curation of extraterrestrial materials. After an initial cataloging to precisely record the samples available, and their mass, volume, and general type, a group of Russian and American scientists carefully divided the whole as they had agreed in the original mission planning, reserving 51% of the material for continued storage in Moscow, with the other 49% being transported to the Lunar and Extraterrestrial Sample Laboratory Facility in Houston for American study.
Naturally, as soon as both laboratories received their final allocations of Phobos material, an intensive process of studying it began. These analyses, first and foremost, gave qualified support to the carbonaceous chondrite theory of the moon’s composition, showing an overall composition far more similar to that type of meteorite than to “black chondrites”. Nevertheless, there were still puzzles in the data; in particular, the core and deep samples, which were expected to show at least some hint of increased water content at depth, remained as stubbornly bone-dry as the surface regolith, leading to suggestions that some catastrophic event early in the moon’s history, perhaps during its formation, had desiccated it, driving all of the water and other volatiles off. Further support for this theory came from the results of careful tracking of the orbiter while it was in close proximity to Phobos, which seemed to indicate fairly significant fluctuations in density throughout the body. In particular, there seemed, from the relatively low-resolution data available, to be distinct “nuggets” of higher-density material contained within a “fluffy” low-density core, which itself was overlaid by a relatively dense surface crust. Several theories have arisen to explain this pattern of densities, but the most popular relates it to the relatively energetic collision of several proto-Phobos bodies of different composition in Martian orbit; most of the material would have remained within the Martian gravity well and eventually recoalesced into one or possibly more successor bodies, Phobos and perhaps Deimos or even other, now lost moons of the planet. Besides mixing materials of several different types, these would have driven out any water that might have been present in the source material, leaving dry and desiccated rock behind. Nevertheless, this theory is not the only contender, and even the continued analysis of samples from the moon has not produced any definitive conclusions.
As with every space mission, Fobos Together had created new mysteries even while it was discovering new facts, revealing Phobos to be a little world just as worthy of study in its own right as any other. Despite their instigation of the mission, however, Russia has no plans to return and try to push the boundaries of our knowledge of the moon further. Instead, buoyed by the unquestionable success of Fobos-Grunt and benefiting from the technical development invested in the mission by not only themselves but also the United States, they have drawn up a range of new missions building on its success: Luna-Grunt, Vesta-Grunt, and, the ultimate prize looming as large in the imagination of Mars planners as it has for the past forty years, Mars-Grunt. While the third remains not much more than paper plans, Luna-Grunt is scheduled for launch in 2016, and Vesta-Grunt by the end of the decade. With a considerable amount of lunar material presently in labs worldwide from the Artemis missions, the purpose of Luna-Grunt is less the mere collection of lunar material and more to show that Russia can, indeed, launch and operate missions, even complex ones, on its own, and its success will be an important step forwards for their program.
I just get to post these, I don't deserve much of the credit beyond helping develop the ideas for them.