Built in 1961, the Spacecraft Assembly Facility at NASA'sJet Propulsion Laboratory in Pasadena, California, is the cradle of roboticspace exploration.

The first probes launched to the Moon, Mars and Venus wereassembled here. So were all of NASA's Mars rovers, Galileo and Cassini (thefirst orbiters to Jupiter and Saturn), and the twin Voyager spacecraft that arescouting the farthest reaches of the solar system. A new rover, Mars 2020, isgoing through final testing in this facility before being shipped in Februaryto Cape Canaveral, Florida, where it will launch this summer.

The Spacecraft Assembly Facility's construction marks whenJPL transitioned from missiles to space exploration, according to JPL historianErik Conway. "It's where all JPL-built missions from 1962 onward were assembled,"he said. "It was originally just one high bay. They added a second in 1976,during the construction of the Voyagers."

The facility's best-known featuresare a pair of eggshell-white clean rooms called High Bay 1 and High Bay 2. Throughthe windows of each room's viewing gallery, visitors can watch engineers gownedin white "bunny suits" testing Earth-observing satellites and robotsbuilt for alien worlds. More than 30,000 members of the public visit HighBay 1 each year, and many also tune in online to see the workgoing on there.

This summer, visitors will be able to see an Earth-sciencemission called NISAR being built inHigh Bay 1. It will be followed by EuropaClipper. High Bay 2 will be home to an Earth-science mission called SWOT before a mission to a metalasteroid, Psyche, takes its place.

What's a CleanRoom?

As the name implies, a clean room has to be pristine: Dust,hair, oils and other particulates in the air can interfere with electronics andmoving parts. All efforts are made to keep bacteria to a minimum as well. Scientistsdon't want to discover life only to find it was accidentally sent from Earth.

"The whole idea of a clean room for spacecraft assemblycomes out of the Ranger program," Conway said.

As pathfinders for the Apollo missions that followed, the nineRanger missions were essentially unarmed missiles fired at the Moon. All butthe first two were built in High Bay 1, back when it looked more like anaircraft hangar; engineers even smoked in it. The standards for manufacturingspacecraft were just being established.

Sterilizing a spacecraft with heat appeared to fry Ranger3's electronics, causing it to miss the Moon by 22,000 miles (35,000kilometers). Debris floating inside Ranger 4 is believed to have led to itsfailure. Engineers began to realize that specialized clean rooms and cleaningprocesses were needed to build successful missions.

"When JPL started, we knew more about spacecraft thananybody else - and we knew nothing," saidArden Acord, a systems engineer who began working at JPL in 1971. "Welearned a lot of things along the way."

Many of his first coworkers had built the Sergeant andCorporal missiles when JPL was still a U.S. Army lab. Acord was aself-described long-haired hippie working alongside guys with crew cuts:"It was a tough club to break into for a while. But eventually I becameaccepted." He went on to help build the twin Viking orbiters, which carriedthe first successful Mars landers, Voyager 1 and 2, and Galileo and Cassini.

Two Rooms for Earthand Beyond

Almost all the spacecraft Acord worked on were built inHigh Bay 1, which in 1973 became what's known as a Class 10,000 clean room.That means there are fewer than 10,000 particles of 0.5 micronsor larger in size per cubic foot of air volume (0.5 microns is about 200 timessmaller than the width of a human hair).

Opened in 1976, High Bay 2 is aClass 10,000 clean room as well. The air in both rooms cycles about 70times per hour through extensive filtration systems. To keep the workerscomfortable, High Bay 2 is kept at 70 degrees, while High Bay 1 is kept at 68degrees.

Deep space missions tend to bebigger and require more ground equipment, so they typically go in High Bay 1and involve more gowning for planetary protection purposes. Being the smallerof the pair, High Bay 2 is more suitable for the spacecraft of Earth sciencemissions. The high bays' hangar-door dimensions determine the maximum size ofthe spacecraft that can be built within.

Keeping It Clean

Of course, filtered air is only part of what makes a cleanroom clean.

"The level of cleanliness changes depending on thespacecraft you're building," said Roger Francis, the building's facilitymanager. "If you have special lenses, like a telescope, it requires moreeffort to make sure particles don't affect your instruments."

But regardless of the type of spacecraft, staff regularlywipe down surfaces with 180-proof isopropyl rubbing alcohol, push microfibermops across the floors and use HEPA vacuums along wall corners, while the wallsthemselves are cleaned up to 10 feet (3 meters) high. Most metal is stainlesssteel, which resists corroding and releasing particles into the air.

Then there are the rigorous procedures required foreverything that enters the clean room.

For spacecraft and their separate components, that meansbeing wrapped in plastic and brought into an airlock outside the clean room. They'reunwrapped on the "dirty side" of the room and wiped down before beingmoved to the clean side.

A crane capable of lifting 30,000 pounds (13,608kilograms) slides along the ceiling of each room, assisting workers as theymove equipment through the high bays. A white parasol on each crane's cablecatches any grease or debris from the crane that could land on the sensitivehardware below.

Dressing the Part

People follow a special process before entering the cleanroom as well: Automated shoe brushes and sticky mats remove debris from theirshoes before they enter a locker room. Once their feet are covered withbooties, they step over a line onto the clean side of the room.

Then it's time to don a bunny suit, face mask, hair coverand latex gloves before taping sleeves closed. (A mannequin called High Bay Bobstands on the floor of High Bay 1, demonstrating proper attire and givingvisitors a sense of scale.) Finally, they step into an "air shower"that blows stray particles off the outside of their garments.

Static electricity can interfere with electronics, so personnelwear an antistatic cord around one wrist, with a clip on the other end toattach to hardware in the clean room. As added precautions against staticelectricity, humidity in the room is kept at about 45% and the concrete floor hasa special epoxy coating to bleed static charge that builds up in garments aspeople move about the room.

The Wall of Fame

The mission emblems that line the top of High Bay 1'ssouth wall aren't exempt from the cleanliness requirements. The idea for theplacards came about in 2008, when Acord was tasked with preserving theSpacecraft Assembly Facility's history. Representing JPL's biggest missions,the emblems would serve as a testament to engineers' hard work assembling andtesting hardware.

Visitors to High Bay 1 may have noticed the south wall is runningout of room for additional placards. But there's always more space to explore: Emblemsmight expand onto the east wall in the future.

News Media Contact

Andrew GoodJet Propulsion Laboratory, Pasadena, Calif.818-393-2433andrew.c.good@jpl.nasa.gov

Alana JohnsonNASA Headquarters, Washington202-358-1501alana.r.johnson@nasa.gov

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Space History Is Made in This NASA Robot Factory - Jet Propulsion Laboratory