Fwd: 20 Years Since STS-59

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From: "Gary Johnson" <gjohnson144@comcast.net>
Date: April 21, 2014 9:46:10 PM CDT
To: "Gary Johnson" <gjohnson144@comcast.net>
Subject: FW: 20 Years Since STS-59

 

 

AmericaSpace

For a nation that explores
April 19th, 2014

Endeavour's Radar Love: 20 Years Since STS-59 (Part 1)

By Ben Evans

 

The Space Radar Laboratory (SRL) payload flew twice in 1994, firstly aboard STS-59 in April and later aboard STS-68 in September-October. The large Shuttle Imaging Radar (SIR)-C is clearly visible in the foreground. Photo Credit: NASA

Twenty years ago this week, the crew of Endeavour on STS-59 demonstrated that the shuttle program was imbued with "Radar Love," as they operated the first Space Radar Laboratory (SRL-1) to acquire unprecedented views of the Home Planet from orbit. For 11 days, astronauts Sid Gutierrez, Kevin Chilton, Jay Apt, Michael "Rich" Clifford, Linda Godwin, and Tom Jones worked around the clock to ensure that the radar instruments of the SRL-1 payload gathered an enormous quantity of scientific data. Much of that data is still being analyzed to this day and has helped to shape our understanding of Earth's past, present, and, potentially, its future.

SRL-1 had its genesis in the Shuttle Imaging Radar (SIR), which first flew aboard STS-2 in November 1981. However, the capabilities of SIR-A were left undemonstrated, because the scheduled five-day mission was cut short by a fuel cell malfunction and shuttle Columbia returned to Earth after just 54 hours. Three years later, however, it flew again aboard Challenger on STS-41G as "SIR-B," and its success provoked astonishment. Over an eight-day period in October 1984, it identified ancient caravan trails in Arabia, allowed geologists to construct three-dimensional maps of subtle features on California's Mount Shasta, permitted contour modeling of parts of eastern and southern Africa, and examined intricate structural features, including fault-lines, folds, fractures, dunes, and rock layers.

By this time, at least two more missions of the shuttle-ferried radar were planned, but had been extensively delayed. On the eve of the Challenger disaster, SIR-C was scheduled to form part of SRL-1 and scheduled for launch on STS-72A in March 1987 from Vandenberg Air Force Base, Calif. The payload would have operated from a near-polar inclination of 88 degrees, offering its radar instruments a broad imaging swathe across most of Earth's landmasses. In the aftermath of Challenger, all Vandenberg missions were suspended (and ultimately cancelled) and the launch site for SRL-1 changed to the Kennedy Space Center, Fla. This meant that the maximum achievable orbital inclination for the mission was 57 degrees. When NASA issued its January 1990 manifest, the launch of SRL-1 was not anticipated before the summer of 1992, and shuttle delays forced an inevitable slip into the last quarter of the following year.

When astronaut Linda Godwin was named as the SRL-1 payload commander in August 1991, the launch of her mission had moved forward slightly to the late summer of 1993. Six months later, "rookie" astronaut Tom Jones joined her as a mission specialist and the pair began a lengthy period of preparatory work on SRL-1, ahead of the assignment of the other four crew members.

The STS-59 crew was tasked with operating a battery of radar instruments around the clock. Left row (front to back) are Tom Jones, Linda Godwin, and Kevin Chilton; right row (front to back) are Jay Apt, Michael "Rich" Clifford, and Sid Gutierrez. Photo Credit: NASA

In his memoir, Skywalking, Jones recounted the news of receiving this first assignment to a space mission. One February morning in 1992, he was summoned to the office of the Director of Flight Crew Operations, Don Puddy, at the Johnson Space Center (JSC) in Houston, Texas. Sat at the conference table with Puddy was Godwin. "I vaguely remembered that Linda had been assigned earlier to work on long-range planning for one of next year's shuttle missions," Jones wrote, "but I couldn't recall which one." Quickly, Puddy asked Jones if he would be prepared to serve as Godwin's "science deputy" on SRL-1. Naturally, it was a question with only one answer, but Jones (who held a PhD in planetary science) would prove an invaluable asset on one of the most dramatic research missions of the decade.

Operating from an orbital inclination of 57 degrees, the payload's imaging radar would map a substantial portion of Earth, including regions as far north as Juneau, Alaska, and a little farther south than Tierra del Fuego at the tip of Argentina. When the remaining four members of the SRL-1 crew—which had by now received the mission designation of "STS-59″—were announced in March 1993, only two of them had previous experience of such a high-inclination orbit—one of the highest ever attained by the shuttle. Mission specialists Jay Apt and Rich Clifford had flown 57-degree orbits on earlier flights and were acutely aware of its usefulness for Earth observations.

In fact, Apt wrote extensively about the experience in his book Orbit, co-authored with Justin Wilkinson and Michael Helfert. "On my first space flight," Apt wrote, referring to STS-37, which operated at an inclination of 28.5 degrees, "I flew no farther north than the glorious Himalaya. I shot photo after photo of Tibet, with the Sun low in the sky and the shadows long. Central and northern Asia were a mystery  to me. On my second and third flights, I was on the flight deck for a 12-hour shift, when it was "night" in Houston and "day" in Asia. We flew over almost the entire continent."

From 57 degrees, Apt saw plumes of smoke from cellulose plants at the south shore of Lake Baikal, irrigation channels cutting across the Taklimakan Desert, multi-coloured soil tones in Kamchatka—the latter of which, he wrote, was "worth the trip up the north"—and the puzzling landscape of the Korean peninsula. Thousands of miles away, in the northern Americas, Apt beheld drifting volcanic ash from Mount Spurr in Alaska, together with the breathtaking grandeur of Yellowstone National Park and the geological variety of the western states. Elsewhere, northern Europe seemed to be almost completely covered by farmland, and during one pass over Australia, on STS-59, a woman on the ground relayed Apt's ham radio signals to enable him to speak directly to cosmonaut Valeri Polyakov aboard the Mir space station. South America was most memorable for Apt, as he was able to see smoke and fires in Tierra del Fuego and Patagonia, presented to his eyes as far-off points of light. Even though he had flown to 57 degrees on STS-47, Apt found that lighting conditions were not good, with the shuttle's windows pointed toward the Sun for most of the time, but SRL-1 benefited from much better conditions. In preparation for the immense amount of photography which would be conducted, alongside the radar observations, all six crew members became proficient in the use of appropriate camera lenses with consistent shutter speeds and light meters to determine proper exposure times.

The STS-59 crew patch. Image Credit: NASA

To understand how the SRL-1 payload evolved, it is important to comprehend the accomplishments of the SIR-A and SIR-B radars. The first mission in November 1981 was restricted to recording the ground-track directly "beneath" the orbiter, but in preparation for SIR-B the radar was engineered to "tilt" at angles of between 15 and 57 degrees to the side and its imaging resolution was enhanced from 130 feet (40 meters) to 80 feet (25 meters). By varying its "look" angle in this fashion, it became possible to assemble "mosaics" of adjacent surface features, collected over periods of several days. The third mission, SIR-C, offered multi-frequency, multi-polarization imagery and represented the first spaceborne radar with the ability to transmit and receive horizontally and vertically polarised waves at both the L-band and C-band wavelengths.

Measuring 39 feet (12 meters) long and 13 feet (four meters) wide and weighing 23,150 pounds (10,500 kg), SIR-C was the most massive piece of flight hardware ever built at the Jet Propulsion Laboratory (JPL) in Pasadena, Calif. It was a "synthetic-aperture" radar and, like a huge dining table, consumed almost half of shuttle Endeavour's payload bay on STS-59. "Synthetic-aperture radar technology," explained Tom Jones in his memoir, "uses the motion of a spacecraft or aircraft to electronically synthesize an antenna much larger than its physical size, yielding higher imaging resolution." Originally assembled from spares left over from NASA's 1978 Seasat mission, SIR-C was affixed to its own truss support structure, which, in turn, was mounted onto a Spacelab pallet, providing a "side-looking" viewing angle, some 47 degrees from the nadir. As a result, during data-gathering operations the shuttle was required to reorient itself to precisely direct SIR-C at its ground targets. Unlike the previous SIR missions, its radar beam was formed from hundreds of transmitters, embedded within the surface of the antenna. By properly adjusting the energy from these transmitted, the beam could be electronically "steered" and, when combined with shuttle maneuvers, offered the scope to acquire images from various directions.

However, SIR-C was not the only radar aboard SRL-1. Running like a strip along the uppermost edge of SIR-C was "X-SAR"—a 39-foot (12-meter) x 1.3-foot (0.4-meter) synthetic-aperture device, built by a partnership of organizations, including the German Dornier and Italian Aleniz Spazio companies, together with the German (DARA) and Italian (ASI) space agencies—which offered a single-polarization radar, operating in the X-band. X-SAR was a follow-on project from Germany's Microwave Remote Sensing Instrument, flown aboard Spacelab-1 in late 1983. Its "slotted waveguide antenna" was finely tuned to produce a narrow energy beam, and X-SAR was designed to be mechanically aligned with the L-band and C-band beams of SIR-C.

Before launch, NASA's SRL-1 press kit noted that resolutions as high as 33 feet (10 meters) were a possibility. Throughout the projected nine-day mission, the combined SIR-C/X-SAR imaging suite was expected to make around 50 hours of observations, covering more than 19.3 million miles² (50 million km²), acquiring 32 terabytes of raw data, and storing it all on 180 cassettes, using three high-density, digital, rotary-head tape recorders. Both radars would work together to acquire the best possible data. For instance, the shorter-wavelength X-SAR data was expected to be particularly useful for the determination of snow types, with the L-band and C-band capabilities of SIR-C estimating snow volumes.

With St. Joseph of Cupertino rooting for them, the crew of STS-59 heads out to the pad on 9 April 1994. Photo Credit: NASA

Although the United States, Germany, and Italy were involved in the development of the payload, more than 50 investigators from 13 nations (Australia, Austria, Brazil, Canada, China, the United Kingdom, France, Germany, Italy, Japan, Mexico, Saudi Arabia, and the United States) provided experiments and investigations as part of the science team. Also operating as part of the payload was an instrument called the Measurement of Air Pollution from Satellite (MAPS), which had also flown as part of the SIR-A and SIR-B missions. It sought to measure global distributions of carbon monoxide in the troposphere, between the altitudes of 3-9 miles (5-15 km), in which the "weather system" is most active, and it had already pointed to a worrisome trend that "greenhouse gases" had become increasingly severe throughout the early part of the 1980s. MAPS also highlighted disturbing levels of pollution—particularly in the tropics—due to the seasonal burning of biomass.

SRL-1 would not be scanning the planet in an indiscriminate fashion. Rather, a series of 19 "super-sites" of particular geological, hydrological, or ecological interest were selected and would be observed during daily radar passes. Experiments were set up on every continent in the world, save Antarctica, and particular regions of focus included Mammoth Mountain, Calif., for remote-sensing of the water content of the Sierra Nevada ice pack; Chichkasha, Okla., for soil-moisture studies; Michigan's Upper Peninsula to investigate forest biomass; together with temperate forests in North America and Central Europe and tropical forests in South America's Amazon basin, surface and internal waves within the Mid-Atlantic Gulf Stream, and Hawaii's Volcanoes National Park. During the SRL-1 mission, "ground truth" teams at various sites undertook measurements of vegetation, soil moisture, sea state, snow cover, and weather conditions to correlate with the shuttle data.

With such an enormous workload of preparation for the mission, it came as something of a relief when in mid-1992 NASA took the decision to shift SRL-1 into the spring of 1994 and move the critical Hubble Space Telescope (HST) servicing mission to the left. In the meantime, early in March 1993, the names of the four astronauts who would accompany Godwin and Jones were announced. Mission specialists Jay Apt and Rich Clifford would be joined by commander Sid Gutierrez and pilot Kevin Chilton; all four had flown before. (In Skywalking, Jones recalled a telephone call from Clifford, with a simple message of unbridled joy: "We're flying together on STS-59, T.J.") Gutierrez soon broke the crew into two shifts—"red" and "blue"—to supervise orbiter systems and the SRL-1 payload around the clock. He would lead the red team, with Godwin and Chilton, whilst Apt would lead the blue team, joined by Jones and Clifford. "He needed the two pilots on the same sleep cycle," Jones explained, "both fresh and wide awake for launch and landing days. Linda would join them, enabling Sid to get the payload commander's input on any experiment or orbiter problems without having to wake the opposite shift."

According to the STS-59 press kit, launch was scheduled for 7 April, but an inspection of a shuttle main engine at Rocketdyne's facility in Canoga Park, Calif., had found that the critical dimensions of nickel-alloy liquid oxygen guide vanes in the turbopump preburner were "out of tolerance." Inspectors found that two components had sharp, rather than rounded, tips, presented an increased possibility of fragmentation … and that enhanced the likelihood of a premature engine shutdown. "A thinned or deformed vane," explained Tom Jones, "could break off in the oxidizer flow, shattering the turbopump blades downstream."

A 24-hour delay was enforced to offer technicians the opportunity to examine Endeavour's vanes, which turned out to be in the proper configuration. The delay proved fortuitous, for Kevin Chilton contracted a virus and had to be placed under observation, "isolated" even from his already-isolated crewmates in quarantine. "It was a race," wrote Jones, "between Chili's recuperative powers and the ticking countdown clock." By the 7th, Chilton had recovered sufficiently to rejoin the rest of the crew. High winds the following morning threatened the launch. Overcast conditions led the Mission Management Team to lengthen the "hold" in the countdown at T-9 minutes, and, eventually, late in the 2.5-hour "window," the clouds began to clear.

Endeavour rockets into the dawn on 9 April 1994. Photo Credit: NASA

From the flight deck, Gutierrez, Chilton, Apt, and Clifford described a beautifully clear blue sky through their windows. Downstairs on the middeck, Godwin and Jones could see nothing, but it seemed a positive change. Unfortunately, this break was accompanied by an increase in wind speed, which exceeded the maximum allowable limit for a Return to Launch Site (RTLS) abort at the Shuttle Landing Facility (SLF). Jones tried to invoke St. Theresa, patron saint of aviators … and, additionally, St. Joseph of Cupertino, the patron saint of astronauts, for their help.

Suddenly, the cabin fell silent. Then Gutierrez spoke. "What's St. Joseph of Cupertino got to do with astronauts?" he asked.

"Well," Jones replied, "he used to levitate over the altar of his monastery chapel. He discovered zero-G three hundred years ago!"

They gave it a try, but alas it was not to be, and the weather gods were just too strong on 8 April 1994. With the winds continuing to gust out of limits, Launch Director Bob Sieck ordered a scrub. Liftoff was rescheduled for 7:05 a.m. EDT on the 9th, and it was six anxious astronauts who climbed aboard Endeavour that morning, as another scrub would produce a conflict with other scheduled launches on the Eastern Range and effect a delay until at least the 23rd. Lying uncomfortably on their backs, they listened to the milestones over the intercom. By 6:56 am, as Endeavour emerged from the last scheduled "hold" in the countdown at T-9 minutes, they tightened their harnesses and steeled themselves for the controlled explosion that would soon come. At  T-5 minutes, Kevin Chilton leaned over from the pilot's seat and flipped a trio of switches to activate the orbiter's Auxiliary Power Units (APUs). Endeavour now had hydraulic muscle.

In the acronym-laden minutes which followed, the astronauts were instructed to close and lock their helmet visors and activate the flow of oxygen into their suits. The Albuquerque-born Sid Gutierrez, the only shuttle pilot of Hispanic ancestry, led his team in their final "comm" checks and was wished "Vaya con Dios"—"Godspeed"—by launch controllers as a last send-off. With 31 seconds to go, they received the "Go" for autosequence start, as Endeavour's computers assumed primary command of vehicle critical functions. Fifteen seconds later, navigational indicators on the instrument panel snapped smartly into their correct launch-ready positions. "Nav init," confirmed Gutierrez.

At seven seconds, the swirling sparks of the hydrogen burn igniters gave way to a familiar rumble and sheet of translucent orange flame, as the three main engines roared to life, quickly reaching full power and producing three dancing Mach diamonds. "Three at a hundred!" yelled Chilton over the growing crescendo. Finally, at T-zero, the twin boosters flared plumes of brilliant orange flame and the STS-59 crew received a smart punch in the back as they departed Planet Earth on a mission to study Planet Earth.

 

Copyright © 2014 AmericaSpace - All Rights Reserved

 

===============================================================

 

AmericaSpace

For a nation that explores
April 20th, 2014

Endeavour's Radar Love: 20 Years Since STS-59 (Part 2)

By Ben Evans

 

Endeavour rockets into the dawn on 9 April 1994. Photo Credit: NASA

Twenty years ago this week, the crew of Endeavour on STS-59 demonstrated that the shuttle program was imbued with "Radar Love," as they operated the first Space Radar Laboratory (SRL-1) to acquire unprecedented views of the Home Planet from orbit. For 11 days, astronauts Sid Gutierrez, Kevin Chilton, Jay Apt, Michael "Rich" Clifford, Linda Godwin, and Tom Jones worked around the clock to ensure that the radar instruments of the SRL-1 payload gathered an enormous quantity of scientific data. Much of that data is still being analyzed to this day and has helped to shape our understanding of Earth's past, present, and, potentially, its future.

As described in yesterday's AmericaSpace history article, SRL-1 had its genesis in the Shuttle Imaging Radar (SIR), which flew aboard two missions in the early 1980s. On STS-2 in November 1981, SIR-A's capabilities were left undemonstrated, because the scheduled five-day mission was cut short by a fuel cell malfunction and Shuttle Columbia returned to Earth after just 54 hours. Three years later, however, it flew again aboard Challenger on STS-41G as "SIR-B," and its success provoked astonishment. Over an eight-day period in October 1984, it identified ancient caravan trails in Arabia, allowed geologists to construct three-dimensional maps of subtle features on California's Mount Shasta, permitted contour modeling of parts of eastern and southern Africa, and examined intricate structural features, including fault-lines, folds, fractures, dunes, and rock layers.

A dedicated SRL-1 payload, incorporating both SIR and a German-built X-Band Synthetic Aperture Radar (X-SAR), had been on the cards since before the Challenger disaster and was originally assigned to fly one of the shuttle's missions from Vandenberg Air Force Base, Calif., into near-polar orbit. The loss of Challenger and the end of operations at Vandenberg, without a single launch, led to a decision to fly SRL-1 from the Kennedy Space Center (KSC) and an orbital inclination no higher than 57 degrees. By 9 April 1994, after two years of training, the six-member crew was ready to go.

The STS-59 crew was tasked with operating a battery of radar instruments around the clock. Left row (front to back) are Tom Jones, Linda Godwin, and Kevin Chilton; right row (front to back) are Jay Apt, Michael "Rich" Clifford, and Sid Gutierrez. Photo Credit: NASA

Writing almost a decade later, in his memoir, Sky Walking, Tom Jones remembered lucidly the adrenaline-charged minutes of his first climb into orbit. A "nasty shaking" was accompanied by a peculiar sensation of the entire cabin whipsawing around him, as the computer-controlled "Roll Program" maneuver, 10 seconds after liftoff, oriented Endeavour for her 57-degree orbit. Jones thought of his father, who had died a little more than a year earlier. Two minutes into the ascent, the twin Solid Rocket Boosters (SRBs) were safely jettisoned and the shuttle continued to power her way into orbit under the thrust of her main engines. At length, Gutierrez and Chilton congratulated Jones as Endeavour crossed the 62-mile (100 km) Kármán line and passed the official boundary between the "sensible" atmosphere and the edge of space.

Suddenly, the G-imposed pressure on his chest was gone, he felt light under his harness straps … and was hit by the instant realization: "This must be weightlessness!" In Skywalking, Jones noted that the sensation of perpetual free-fall was perplexing, but that he encountered no difficulties deciding which way was "up" and which was "down." Then, as his body adapted to microgravity, fluids normally pulled into his legs and lower abdomen instead migrated toward his chest and his inner-ear balance organs sent confusing messages to his brain … and produced a wave of nausea.

It came, he wrote, as a sudden doubled-over spasm, eyes closed, feeling miserable, and was gone within minutes. A shot of the anti-nausea drug Phenergan from crewmate Rich Clifford provided instant relief, but the malaise would return to haunt Jones a couple of times during the early stages of the flight. Yet the view of Earth was glorious. "As Endeavour rose toward sunrise, I gasped," he wrote. "Between heaven and Earth was a vision of pure beauty, the robin's-egg-blue of the atmosphere backlighting the darkened horizon." For an instant, his eyes filled with tears.

The Space Radar Laboratory (SRL) payload flew twice in 1994, firstly aboard STS-59 in April and later aboard STS-68 in September-October. The large Shuttle Imaging Radar (SIR)-C is clearly visible in the foreground. Photo Credit: NASA

But the clock was forever their enemy. As time ticked down toward the first sleep period for the blue team, Linda Godwin's red shift led the activation of SRL-1. Despite initial problems with the power-up of the X-SAR amplifier—caused by an overly sensitive protection circuit—the German-built radar entered full operations on 10 April. Although the mission had always been baselined for nine days, it was expected that with appropriate use of consumables, a 10th day could be squeezed out of Endeavour. The decision to extend STS-59 did not drag its heels and came late on Day One, setting the mission on its path of science-gathering discovery in fine fashion.

The astonishing experience of 16 sunrises and sunsets in each 24-hour period was best illustrated through one of Tom Jones' written recollections. Orbiting at twice the average shuttle inclination, and a much lower altitude of just 136 miles (220 km), he and his crewmates were provided with an astonishing vista of the Home Planet. "Now the eggshell-blue light of the sunrise is coating the horizon," he wrote at one point, late in the mission. "The payload bay is now going bluish-white as we come up out of the darkness. Across Nova Scotia now, and Labrador, and still no sunshine visible. I can still see the stars. No, not for long. Here comes the orange of the Sun. Boom! Sunrise! Now the payload bay is pink-orange, yellow, going to white, and it will soon be brilliant. Fantastic!"

Amidst all the high technology and intensive science workload, it was a profoundly spiritual experience. On the second Sunday after Easter, Jones, Chilton, and Gutierrez—all Catholics, and Chilton a Eucharistic minister—gathered on the flight deck for a short service of Communion. They also had the opportunity, on 16 April, to speak via the Shuttle Amateur Radio Experiment with fellow astronauts Norm Thagard, Bonnie Dunbar, and Ken Cameron, who had recently moved to Russia to support the early Shuttle-Mir effort.

Overall, SRL-1 was a remarkable scientific triumph. In its post-flight mission report, NASA announced that the SIR-C/X-SAR observations had accomplished 97 percent of their required data takes from 400 primary science targets and 99 percent from the 19 critical super-sites. The crew also handled additional requests, including imaging Germany's Rugen Island, in the Baltic Sea, and examining Japanese rice fields. Ninety-four hours of radar data, taken over 44 discrete nations and covering an area in excess of 27 million miles² (70 million km²), were stored on 165 of the digital tapes. Elsewhere, the Measurement of Air Pollution by Satellite (MAPS) experiment performed flawlessly, acquiring data on the regrowth of forests in a fire-scarred area of China. On one occasion, Jones verbally report on thunderstorms over Taiwan, the Philippines, and New Guinea to augment the MAPS data.

Jay Apt performs Earth resources photography through Endeavour's flight deck windows. Photo Credit: NASA

On 19 April, the payload bay doors were closed and sealed on time, but cloud conditions at the Shuttle Landing Facility (SLF) at KSC caused the first scheduled landing attempt of the day to be waved off, just half an hour before the anticipated de-orbit burn. "Unfavourable and dynamic" weather later that afternoon also put paid to a second attempt to bring STS-59 home. This forced mission managers to reschedule the landing for the following day, the 20th. However, weather at KSC remained "No-Go," and Gutierrez and his crew were diverted to Edwards Air Force Base, Calif., touching down without incident at 9:54 a.m. PDT on concrete Runway 22, after a mission lasting a little more than 11 days. STS-59 had proven a spectacular success, gathering sufficient data to fill an estimated 20,000 encyclopedias, taking more than 15,000 photographs, and requiring in excess of 400 maneuvers to position the shuttle for the radar observations.

Two weeks later, with the ink barely dry on their crew flight report, Tom Jones returned to his office at the Johnson Space Center (JSC) in Houston, Texas, to begin his next assignment. More than two years of his professional life at NASA had been devoted to the Space Radar Laboratory, and in August 1993 he had been assigned to serve as payload commander for the second flight, SRL-2. The Jet Propulsion Laboratory (JPL) of Pasadena, Calif., which developed the radar, wanted two of its own experts to serve as payload specialists, but had been told that NASA career mission specialists could handle the tasks. Next, JPL insisted that at least one crew member should fly both missions.

This followed typical NASA practice of "carrying over" an experienced crew member from one payload to the next on important science flights … but Jones' transition from SRL-1 to SRL-2 offered something a little different. Originally, the two radar flights were supposed to fly at least a year apart, as shown by NASA's February 1991 and January 1992 manifests, which anticipated a 15-month gap between them. However, when the decision was taken, in mid-1992, to advance Endeavour's Hubble repair flight ahead of SRL-1, the two missions drew much closer—within four months of each other—on the manifest.

Twenty years ago today, on 20 April 1994, Endeavour made landfall at Edwards Air Force Base, Calif., at the end of STS-59. Photo Credit: NASA

By the time Jones was named as the SRL-2 payload commander, he was still almost eight months away from flying SRL-1. "I recalled my surprise," he wrote in Skywalking, "when I met with chief astronaut Robert "Hoot" Gibson … He had just invited me to fly again." By then, the manifest envisaged SRL-2—aboard STS-68—flying aboard Endeavour in mid-August 1994, a mere four months after SRL-1. "Hoot laughed at my startled reaction," Jones continued, "but he wasn't kidding. What else could I say but yes?" Two months later, in October 1993, NASA announced the names of the remainder of the STS-68 crew: Mike Baker in command, joined by pilot Terry Wilcutt and mission specialists Steve Smith, Dan Bursch, and Jeff Wisoff. The five men had pestered Jones mercilessly during his SRL-1 training and even whilst he was in orbit.

"Don't forget you start sims with us next week," read one note, authored by Baker. It was signed off with simplicity: "Your STS-68 Associates."

Little did any of them realize that SRL-2 would only get off the ground after a particularly hair-raising on-the-pad engine abort, less than two seconds ahead of liftoff.

 

Copyright © 2014 AmericaSpace - All Rights Reserved

 

===============================================================