Twenty-five years ago today, on 4 May 1989, Shuttle Atlantis thundered into orbit on a remarkable mission which would unveil the planet Venus—nicknamed Earth’s “twisted sister”—in a wholly new light. During their four days in space, the STS-30 crew of Commander Dave Walker, Pilot Ron Grabe, and Mission Specialists Mark Lee, Norm Thagard, and Mary Cleave deployed NASA’s Magellan spacecraft on a 15-month voyage to Venus. Following its arrival at the mysterious, cloud-shrouded world in August 1990, Magellan spent four years mapping over 98 percent of Venus’ surface using powerful synthetic aperture radar. As described in yesterday’s AmericaSpace history article, the genesis of Magellan was a difficult one, and in January 1986, following the tragic loss of Challenger, it found itself in need of a new booster and a new means of reaching its target.
The cancellation of General Dynamics’ Centaur-G Prime liquid-fueled booster came as a hammer blow for the Magellan project, for if the mission was to continue it would require a new booster to carry it across the vast interplanetary gulf from Earth to Venus. In addition to a new booster, the solution encompassed a different trajectory design. Boeing’s solid-fueled Inertial Upper Stage (IUS) was ultimately pressed into service, although it was far less powerful than the Centaur. With the resumption of shuttle flights scheduled for late 1988, the next available launch “window” to reach Venus under the most optimum conditions came in October 1989. That date quickly became untenable, for it was needed by the Galileo mission, whose own trajectory to Jupiter involved a gravity-assisted boost from Venus.
Consequently, Magellan’s trajectory specialists settled on a four-week window of opportunity which extended from 28 April until 28 May 1989. The trajectory design was known as a “Type IV Heliocentric Orbit,” which required Magellan to complete 1.5 circuits of the Sun, before arriving at its destination in August 1990, but offered the advantages of lower launch energy and Venus approach speed. It also meant that the spacecraft would approach the planet over its north pole and perform mapping swathes in a north-to-south direction, which was the reverse of that planned on the basis of an original 6 April 1988 launch on STS-81I.
With this in mind, STS-30 was targeted to head into space on the opening day of the Venusian window, 28 April 1989. The crew had been assigned more than a year earlier, in March 1988, and for the most part consisted of the original team members assigned to the 61G Galileo mission: Dave Walker in command, Ron Grabe as pilot, and Norm Thagard as the center-seat flight engineer. James “Ox” van Hoften had resigned from NASA and was replaced by Mary Cleave, whilst the final mission specialist place went to Mark Lee.
In the wake of Challenger, Cleave and Lee worked closely together on techniques for payload deployments from the shuttle, and when they were assigned to STS-30 they took primary responsibility for the release of Magellan and its IUS booster. “I never expected to get assigned that fast after the accident,” admitted Cleave, who had flown aboard Atlantis on STS-61B, a few weeks before Challenger, “so I was really surprised when they assigned Mark Lee and I to do this Magellan deployment. It was the first time we deployed a spacecraft that was going to another planet from the shuttle.”
One of the biggest issues was going from a lightweight flight garment on 61B to a bulky and uncomfortable orange-colored partial-pressure suit, with limited cooling, on STS-30. Comparing the two missions, Cleave felt that her first flight was “really loose,” with the astronauts clowning around and having a good time, but on STS-30 all that had changed. It was safer, she said, but much more serious. In their early training, Cleave asked Lee where he wanted to fly for ascent. Lee picked the flight deck, and it was therefore Cleave’s responsibility to take the seat in the darkened middeck, with the duties of handling the escape pole, if necessary, only a wall of lockers for company … and an excuse to make as much noise as she liked! Whereas some astronauts would loathe the middeck seat during ascent, considering it to be claustrophobic, Cleave enjoyed it. “I could hoot, I could holler,” she said, “I could have a marvelous time … and, man, that’s a ride! It’s really a great ride.”
Cleave’s great ride was a few days in coming. The countdown had proceeded normally toward a liftoff on 28 April, but the clock stopped at T-31 seconds when a hydrogen recirculation pump—responsible for cooling Atlantis’ three main engines—developed a short circuit and stalled. The problem was reviewed and another issue with the abnormal venting of a hydrogen circulation line was also rectified, and launch was rescheduled for the start of a 64-minute “window” on 4 May. (The length of these windows, wrote Tim Furniss in Flight International, extended slightly as April progressed into May. The window on 28 April lasted for barely 18 minutes, whilst those from the middle of May through to the close of the Venus window on 28 May increased to a maximum of 121 minutes. This was dictated by the need for daylight landing opportunities at the Transoceanic Abort Landing sites.)
The day of the second launch attempt dawned dreary and overcast, with strong crosswinds blowing across the Shuttle Landing Facility (SLF). Nonetheless, the five astronauts were strapped into their seats, although the countdown clock was held at T-5 minutes, just before the activation of the Auxiliary Power Units (APUs), to wait out the weather. It seemed as if another scrub was inevitable … and then, 59 minutes into the window, the winds dissipated, the clouds parted, and Atlantis rocketed into orbit at 2:46:59 p.m. EST. “As a result of our first scrub, the attitude in the cockpit was relatively relaxed,” Ron Grabe remembered later. “Of course, there’s a limit to how relaxed you can be when someone lights off that big torch beneath you!”
Deployment of Magellan got underway almost immediately. In Cleave’s mind, as soon as it left the payload bay, responsibility passed from the Johnson Space Center (JSC) in Houston, Texas, to the Jet Propulsion Laboratory (JPL) in Pasadena, Calif., and the longer it remained aboard Atlantis, the more chances existed for problems to develop. “Get rid of this thing,” she told the NASA oral historian. “First day, it’s outta there!” The release occurred at 9:01 p.m. EST, a little more than six hours into the mission. Ten minutes later, Magellan’s paddle-like solar arrays were deployed, after which a pair of burns from the IUS booster set the spacecraft on course for Venus. Over the next year, Magellan fired its own thrusters on three occasions to remain on track for the correct arrival time.
That arrival came on 10 August 1990, kicking off one of the most spectacular episodes of planetary exploration ever accomplished. For the next four years, Magellan acquired detailed radar data of craters, volcanoes of various kinds, flat plains, hills, ridges, and other geological formations on Venus. Five “cycles,” each lasting approximately one Venusian “year,” or 224 Earth-days, were completed, acquiring radar imagery and gathering gravitational data. Toward the end of its life, in the summer of 1994, the spacecraft was used as part of “aerobraking” tests to examine atmospheric densities at differing altitudes. Magellan was finally commanded to burn up in the Venusian atmosphere in October 1994, ending a mission which far exceeded all scientific expectations. In total, the project cost $680 million and had mapped almost the entire surfaceat a resolution 10 times better than the earlier Soviet Venera space missions.
All of this was in the future for the crew of STS-30, who spent the remainder of their four-day mission performing scientific experiments, including the Fluids Experiment Apparatus (FEA), under Cleave’s supervision, which produced indium crystals. Cameras were also used to record storm systems and lightning, and Atlantis herself was utilised as a calibration target for electro-optical sensors at the Air Force’s Maui Optical Station in Hawaii. On 7 May 1989, the day before landing, one of the shuttle’s four General Purpose Computers (GPCs) failed and Cleave and Lee, as the designated in-flight maintenance specialists, replaced it with a backup. The mission ended in spectacular fashion at 12:43 p.m. PST (3:43 p.m. EST) on the 8th, when Dave Walker guided his ship to a smooth touchdown on the concrete Runway 22 at Edwards Air Force Base, Calif. Original plans to land on the dry lakebed, Runway 17, had earlier been called off, due to high crosswinds. Their four-day mission had been an enormous success, and its long-term result was that, for much of the next decade, Venus was mapped and understood in far greater detail than our own world, Earth.
This is part of a series of history articles, which will appear each weekend, barring any major news stories. Next week’s article will focus on STS-49, a dramatic satellite rescue and repair mission from May 1992, which also marked the maiden voyage of Shuttle Endeavour.