The Future That Never Came: Planetary Missions of the 1980s

In the days before the internet, the primary means of getting information about space exploration was in books and print periodicals. And back in those days I would regularly look for the latest books with new information on space exploration at the local book stores (you know, the places that sold books before the invention of Amazon.com). A couple of weeks after I had graduated high school in June 1980, I remember finding a new paperback by Robert Powers – the just-published, revised edition of Planetary Encounters: The Future of Unmanned Spaceflight. In addition to presenting a good synopsis of the history of planetary exploration up to that point, the book also included extensive discussions of potential future missions to the planets that were in various stages of study and development at the end of the 1970s. At this time, such information was very hard to come by for a young space exploration enthusiast like myself and this was a welcomed find.

With a fair amount of free time on my hands during the summer leading up to my first semester in college, I read through this book several times to get all the latest details of the various missions that were already underway: the ongoing Pioneer Venus mission, the Viking mission to Mars, the Voyager results from Jupiter and the latest about the Pioneer 11 encounter with Saturn the previous year. I also devoured all of the details about the upcoming Voyager mission at Saturn, the progress on the Galileo orbiter/probe mission to Jupiter, the latest studies of an American rendezvous mission to Comet Halley and many more proposed missions then under study.

What I did not realize at that time in 1980 was that the Golden Age of planetary exploration that I had grown up in was already coming to a quick end. Voyager would continue on to Saturn and beyond but the Galileo mission would experience years of delays relating to issues surrounding its launch on the Space Shuttle. And with the cost overruns from the Space Shuttle coupled with shrinking Federal budgets for science, none of the other proposed projects that I read about in 1980 flew as proposed. Much to my disappointment over the years to come, the dreaded “Great Hiatus” in planetary exploration of the 1980s was just starting.

I recently dug out Powers’ book and looked at it once again with a third of a century’s worth of hindsight. I remembered all the promise of those times and the disappointment of how things turned out after years of budget cuts and missed opportunities. I am also reminded of the potential impact of today’s cuts in spending on planetary exploration after a second “Golden Age” of exploration over the past couple of decades. What follows is a synopsis of what might have been during the 1980s based on the mission “wish list” in Powers’ book and how it has actually turned out.

Mercury

In 1980, only about half of Mercury had been mapped by Mariner 10 during a trio of flybys a half dozen years earlier. Among the possible missions that Powers examined, none had been funded. A flyby using a Venus gravity assist in 1982 just as Mariner 10 had used could have flown a repeat of this mission allowing a portion of the half of Mercury that was unobserved at close range to be examined. The general feeling was that an orbiter mission in 1984 was a better bet and would allow the entire planet to be mapped.

Artist depiction of NASA’s MESSENGER spacecraft in orbit around Mercury. It reached Mercury 26 years later than predicted in 1980. (NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington)

As it turned out, Mercury was a fairly low priority target and it would be 2004 before NASA’s MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) was finally launched for this long awaited Mercury orbiter mission. MESSENGER entered orbit in March 2011 (a quarter of a century after Powers had written) after a series of flybys of Earth (once), Venus (twice) and Mercury itself (three times) used to shape the spacecraft’s orbit and minimize the delta-v required to enter orbit. With the end of MESSENGER’s mission, only ESA’s BepiColombo mission is currently slated to go to Mercury. Scheduled for launch in April 2018, BepiColombo will use a combination of a solar electric ion propulsion system as well as flybys of Earth (once), Venus (twice) and Mercury (five times) to deliver a pair of orbiters in 2024 to continue the exploration of Mercury from above. No lander or sample return missions to Mercury are under serious consideration at this time even after a third of a century.

Venus

When Powers’ book was published in 1980, America’s Pioneer Venus Orbiter mission was still active in orbit around our sister planet. Only the Soviet Union had actually landed probes on Venus at this point in time starting in 1970. The successful Venera 13 and 14 lander missions were launched in the fall of 1981 which were followed by the last lander missions to date, VEGA 1 and 2, which reached Venus in June 1985 carrying balloons in addition to the landers.

The proposed VOIR (Venus Orbiter Imaging Radar) mission was meant to generate a high-resolution map of Venus using the latest synthetic aperture radar techniques first demonstrated by NASA’s SEASAT mission. Unfortunately, the incoming Reagan Administration decided in 1981 to cut NASA’s budget and directed that a planetary mission be cancelled. With Galileo well underway, VOIR was the only choice. In 1983, a significantly scaled down Venus Radar Mapper (VRM) that cut costs by using spare flight hardware from earlier programs was proposed and in 1985 it was renamed Magellan. But before Magellan could fly, the Soviet Union launched Venera 15 and 16 in June 1983 which mapped most of the northern hemisphere of Venus to one-kilometer resolution from orbit.

The Magellan radar mapper being prepared for launch. Magellan (which replaced the earlier and more expensive VOIR mission) reach Venus seven years later than it had been predicted in 1980. (NASA/JPL)

After delays resulting from the Space Shuttle Challenger accident of 1986, Magellan was finally launched from the Space Shuttle Atlantis during the STS-30 mission in May 1989 reaching Venus 15 months later (seven years after the VOIR arrival date predicted in 1980). Since Magellan completed its mission at Venus in October 1994, only the ESA’s Venus Express (which was launched in 2005) and Japan’s Akatsuki (which initially failed to enter orbit in 2011  – see “A Brief History of Planetary Orbit Insertion Failures”) orbiter missions have been sent to Venus. Although there has been some discussion of new Russian missions to land on Venus, no other missions are currently being seriously considered.

Mars

When Powers’ book came out in 1980, the Viking spacecraft had already completed their primary missions almost four years earlier. The Viking 2 orbiter had ceased functioning in 1978 and contact with the lander had been lost in April 1980. The Viking 1 orbiter was about to fall silent in August 1980 but the lander soldiered on until an operator error prematurely ended its extended surface mission in November 1983. There was some talk in the late 1970s of flying a “Viking 3” mission possibly with a primitive roving capability. But by 1980, efforts at JPL primarily centered on developing rover technology for a new dedicated rover mission.

The Sojourner rover arrived on Mars on July 4, 1997. This first Mars rover reached the Red Planet over a decade later than had been predicted in 1980. (NASA/JPL)

Unfortunately, these plans were delayed because of budget cut backs. Eventually, increased budgets coupled with less expensive approaches to planetary exploration were considered starting with the Observer program which sought to adapt proven Earth satellite systems for planetary mission to reign in costs. After years of delays and cost overruns, Mars Observer was launched in September 1992 only to fail upon reaching Mars (see “A Brief History of Planetary Orbit Insertion Failures”). This failure was followed by the Mars Global Surveyor which successfully entered Martian orbit in September 1997. This had been preceded by the Mars Pathfinder engineering flight that landed on Mars on July 4, 1997 carrying the small Sojourner rover (over a decade later than Powers’ predicted – see “First Pictures: NASA’s Mars Pathfinder – July 4, 1997“). These missions have been followed by a more or less steady stream of orbiter and lander missions including three more rovers of increasing sophistication. While the desire to fly a Mars sample return mission continues, there are still no firm missions planned even after all this time.

Asteroids

While asteroid flyby missions were certainly possible using 1980-era technology, asteroids simply were not a high priority especially as funding cuts threatened missions to scientifically more important targets. In the United States, the limited funding for planetary missions in the early 1980s was funneled into the ever-delayed Galileo mission to Jupiter. While the Soviet Union had considered the possibility of a flyby mission past 4 Vesta in the mid-1980s, no asteroid missions ever materialized.

In the wake of the Space Shuttle Challenger disaster in 1986, the Centaur upper stage was no longer available forcing Galileo to switch to the less capable (but somewhat less dangerous) IUS solid upper stage and a more circuitous route to Jupiter involving multiple gravity assists of Venus and the Earth. Fortuitously, this longer path allowed Galileo to flyby the asteroid 951 Gaspra in October 1991 and 243 Ida in August 1993. The first dedicated asteroid mission was NEAR (Near Earth Asteroid Rendezvous) launched in 1996. Instead of a simple flyby of 433 Eros, NEAR (later to be called NEAR-Shoemaker) would use an Earth gravity assist and a capable propulsion system to rendezvous with the asteroid for a one year mission in orbit. Unfortunately the initial attempt to rendezvous in January 1999 failed but NEAR was able to recover and enter orbit around Eros on Valentine’s Day 2000 (see “A Brief History of Planetary Orbit Insertion Failures”). NEAR ended its mission one year later with a landing on the surface of Eros.

The NEAR spacecraft being prepared for launch on the first dedicated mission to an asteroid. NEAR would finally reach 433 Eros on Valentine’s Day 2000. (NASA/APL)

The largest of the asteroids, the dwarf planet 1 Ceres, never had its planned flyby mission. But NASA’s Dawn mission reached Ceres in April 2015 (about 32 years after the optimistic prediction of 1980) following a 2½-year journey from Vesta. And just as it did at Vesta, Dawn would use its ion propulsion system to enter orbit around Ceres for an extend period of observation.

The next part of this article (which can be accessed here) covers the missions to the worlds of the outer solar system and comets that were hoped for in 1980.

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Related Reading

“NASA’s Unintentional Venus Lander”, Drew Ex Machina, June 13, 2016 [Post]

“A Brief History of Planetary Orbit Insertion Failures”, Drew Ex Machina, February 15, 2020 [Post]

“First Pictures: NASA’s Mars Pathfinder – July 4, 1997”, Drew Ex Machina, July 4, 2022 [Post]

“Cruisin’ The Solar System: The Past and Future of Planetary Exploration” (cover story), Ad Astra, Volume 12, Number 2, pp. 25-29, March/April 2000 [Submitted draft]

General References

Robert M. Powers, Planetary Encounters: The Future of Unmanned Spaceflight (Revised Edition), Warner Books, 1980

Paolo Ulivi with David M. Harland, Robotic Exploration of the Solar System Part 1: The Golden Age 1957-1982, Springer-Praxis, 2007

Paolo Ulivi with David M. Harland, Robotic Exploration of the Solar System Part 2: Hiatus and Renewal 1983–1996, Springer-Praxis, 2009