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Uncovering the Secrets of the Ranger 7

Posted on Tue, July 31, 2018
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  • During conservation of the Museum's Ranger 7 spacecraft, we uncovered some unexpected details about the object.
  • The Museum's Ranger 7 weighs in at over 800 pounds, and is fully instrumented with 6 TV cameras. 
  • The Ranger spacecraft pre-date the Apollo program and were designed to take close-up images of the Moon's surface. The predecssors to Ranger 7 faced technical challenges along the way.

As you may have heard, the National Air and Space Museum has set out to revitalize its building on the National Mall and, in the process, transform its exhibits. One of the new galleries will be called Destination Moon and will be devoted to the history and future of lunar exploration. One of the artifacts we are preparing for the new gallery is our Ranger Block 3 spacecraft. We recently took the spacecraft down from where it used to hang in the building and began the process of cleaning it, inside and out.

As a space history curator at the Museum, I am responsible for the artifacts in our collection related to planetary science and exploration. Most of these artifacts have been here for much longer than I have. Every time we take one off display and I get to touch a piece of space history (with gloves, of course), I learn more about it.

The goal of the Ranger series was to acquire close-up images of the lunar surface – something that, when the program began, had never been done before.

Our Ranger came to us in 1977, just one year after the Museum opened to the public. It was built by engineers at NASA’s Jet Propulsion Laboratory (JPL) from real parts used on test vehicles constructed during the Ranger program, and was previously displayed at JPL to celebrate its role in exploring the Moon. It was transferred to the Museum at the suggestion of William Pickering, who ran JPL for 22 years and was one of the people responsible for the Ranger program. Pickering wanted the Museum to be able to display the first successful American robotic mission to the Moon. The spacecraft has remained on display since its arrival.

When we moved Ranger into conservation, conservator David Blanchfield and I were given the rare opportunity to see it up close and examine what real parts JPL had included. The main body of the spacecraft, consisting of the hexagonal aluminum bus and camera tower, arrived as one piece. JPL had already prepared the spacecraft for hanging – all the Museum had to do was attach the solar panels and antenna and it was ready for display. As far as I can tell from looking at the records, no one ever looked inside of the spacecraft to see if it had any real “guts.” It was a good guess that it did have something inside of it – it weighs almost 800 pounds!

Ranger Lunar Probe (A197709930000)

Built between 1961 through 1965, the Ranger spacecraft were designed to give scientists their first detailed closeup images of the lunar surface. The spacecraft were built to crash into its surface, collecting images as they approached. After six failed attempts, Rangers 7, 8, and 9 successfully completed their 65-hour journeys to the Moon. Highlighted in this image are the solar panels on the Ranger spacecraft.

David began his examination of the model in October 2017. He evaluated the model’s condition, finding it to be in good shape but a little dirty from hanging in the Museum for years. Everything was pretty much as expected. About a month after this initial examination, David sent me an email telling me he had made an exciting discovery. While he was cleaning the dust from the camera bay, he discovered that there are six complete TV cameras inside. He also could see, looking deeper into the bay, that there was a lot of electronic equipment, too. When it was hanging from the ceiling, none of this had been visible.

After this discovery, David removed one of the panels of the spacecraft’s camera tower. Inside he found what looked like a very complete set of camera electronics, all bearing the stamp of the RCA company that built the camera system. He sent me photos of his discoveries, taken with his phone camera. It seemed that our model was actually a very complete example of the Ranger spacecraft. Even the “bus” (or main body) of the spacecraft seemed to be fully instrumented (aside from fuel tanks and batteries).

This was an incredible find. The camera system from the Ranger Block 3 was a marvel of engineering, and its significance as the first American camera to take close-up images of the lunar surface makes it a milestone in the history of planetary exploration. David and I decided that we should have one of the Museum’s photographers come and document this discovery, before the spacecraft was reassembled and put back on display.

Museum conservator David Blanchfield and space history curator Matt Shindell examining the Ranger 7 spacecraft

Museum conservator David Blanchfield and space history curator Matt Shindell examining the Ranger 7 spacecraft in the Mary Baker Engen Restoration Hangar at the Steven F. Udvar-Hazy Center, Chantilly, Virginia. Credit: National Air and Space Museum

In April 2018, Museum photographer Eric Long visited us in conservation and took these images of the interior of Ranger’s television camera tower. In them, you can see all six of the lenses from the narrow- and wide-angle cameras that the Ranger Block 3 carried. You can also see all of the intricately wired electronic components that made up the camera system. If you can remember what a television camera looked like in the early 1960s, and how big they were, then you can imagine the engineering challenge RCA and JPL faced in having to fit six cameras inside of this tower.

Looking at these images, I can only conclude that David is right: This is a fully-instrumented Ranger camera tower. It was likely used to test the camera design and function.

Lunar Probe, Ranger, Block III (A19770993000)

Built between 1961 through 1965, the Ranger spacecraft were designed to give scientists their first detailed closeup images of the lunar surface. The spacecraft were built to crash into its surface, collecting images as they approached. After six failed attempts, Rangers 7, 8, and 9 successfully completed their 65-hour journeys to the Moon. Highlighted in this image are the cameras lens on the Ranger spacecraft.

The Story of Ranger 7 (and the six failures that preceded it)

Today we take planetary missions almost for granted. Our ability to visit and explore other worlds has improved by leaps and bounds since our first robotic steps off of our Earth, even while the endeavor remains costly and challenging. So, it is difficult to imagine just how nervous the engineers, scientists, and administrators of the Ranger mission were on July 28, 1964, when they launched Ranger 7 on its way to the Moon. They were nervous because all of the previous six ranger missions had failed.

The goal of the Ranger series was to acquire close-up images of the lunar surface – something that, when the program began, had never been done before. And the spacecraft built for this purpose were designed not to land on the Moon – at least not softly – but to crash into its surface, collecting images as they approached. The spacecraft were designed at the Jet Propulsion Laboratory (JPL) in Pasadena, California. The JPL engineers knew there was a lot they needed to learn in order to pull off this complex mission: They would need to successfully launch the spacecraft on top of a rocket powerful enough to send it to the Moon. They would need to control the spacecraft and navigate the trajectory to the Moon. They would need to design on-board computers that could control the spacecraft’s descent, as well as the collection and transmission of the data collected. In order to develop and test all of the necessary systems and capabilities, JPL decided that the program would have three different phases with three different spacecraft designs, or “blocks.”

Lunar Probe, Ranger, Block III (A19770993000)

Built between 1961 through 1965, the Ranger spacecraft were designed to give scientists their first detailed closeup images of the lunar surface. The spacecraft were built to crash into its surface, collecting images as they approached. After six failed attempts, Rangers 7, 8, and 9 successfully completed their 65-hour journeys to the Moon. Highlighted in this image are the cameras electronics on the Ranger spacecraft.

The first phase of the Ranger series, “Block 1,” was designed to test the Atlas/Agena launch vehicle, putting a Ranger spacecraft in Earth orbit where its equipment could be tested. The second phase, “Block 2,” would build on the lessons of Block 1 and send three spacecraft to the Moon where they would collect images and data and send it back to Earth. The Block 2 Rangers each carried a television camera for collecting images, a gamma-ray spectrometer for studying the minerals in the lunar rocks and soil, and a radar altimeter for studying lunar topography. These spacecraft also carried a capsule containing a seismometer and transmitter that would be able to operate for up to 30 days after being dropped on the lunar surface. The final phase, “Block 3,” consisted of four spacecraft that each carried a high-resolution television camera system, which consisted of six televisions cameras with wide- and narrow-angle capabilities.

If you’re counting, you’ll have noticed that Ranger 7 would fall in Block 3, as the second spacecraft in that phase. So what happened to Rangers 1-6? How had all of the spacecraft in Blocks 1 and 2 failed?

During its final 17 minutes of flight, the spacecraft sent back 4,308 images of the lunar surface.

During Block 1, much of the technology being tested was new. This was true of the Atlas/Agena launch system used to put the two Block 1 spacecraft into orbit. Ranger 1 and Ranger 2 were launched into low-Earth orbits that unfortunately did not last long enough for the spacecraft to stabilize themselves or point their large solar panels toward the Sun to generate power.

Although none of the Block 2 Rangers succeeded in accomplishing their full missions, the three spacecraft together did demonstrate that the launch system and the spacecraft design were sound. Ranger 3 launched perfectly but, due to a malfunction in the guidance system, missed the Moon. Ranger 4 also launched perfectly, and even managed to crash into the lunar surface, but, due to a computer failure, the spacecraft did not extend its solar panels and stopped operating before reaching the Moon. Ranger 5 again missed the Moon, this time because of a power failure that left it inoperable. While these three missions showed progress in working out the bugs of a lunar mission, no significant scientific data was collected. As promising as it was, this did not bode well for a $170 million project. In the meantime, the Soviet Union had successfully landed Luna 2 on the Moon in 1959 and had photographed the far side of the Moon with Luna 3 that same year.

Lunar Probe, Ranger, Block III (A19770993000)

Built between 1961 through 1965, the Ranger spacecraft were designed to give scientists their first detailed closeup images of the lunar surface. The spacecraft were built to crash into its surface, collecting images as they approached. After six failed attempts, Rangers 7, 8, and 9 successfully completed their 65-hour journeys to the Moon. Highlighted in this image are the cameras on the Ranger spacecraft.

A lot was riding on the success of the Block 3 Rangers. Because of the earlier failures, every instrument but the camera system (impressive in its own right) was removed from its design. Things seemed to go very well for Ranger 6. It was launched into Earth orbit by the Atlas rocket and then boosted into a lunar trajectory by a second Agena burn. Ground control successfully sent it course correction instructions, and the spacecraft responded appropriately. The spacecraft crash-landed as intended, with the proper orientation to send data back to Earth. And yet, when it came time to transmit data, there was radio silence. No camera data was returned. NASA convened a review panel that determined the problem to be a malfunction of the camera system most likely caused during launch.

A special team of engineers from JPL were sent to work with the engineers from RCA who designed the camera system. Likewise, RCA gathered a large team of engineers and specialists. Together they worked around the clock to examine every aspect of the camera system to make sure that Ranger 7 would not experience the same problem. NASA sent a team of engineers to JPL to oversee testing of the Ranger 7 spacecraft. Each team double-checked the work of the others. The spacecraft was inspected and tested multiple times before launch.

Lunar Probe, Ranger, Block III (A19770993000)

Built between 1961 through 1965, the Ranger spacecraft were designed to give scientists their first detailed closeup images of the lunar surface. The spacecraft were built to crash into its surface, collecting images as they approached. After six failed attempts, Rangers 7, 8, and 9 successfully completed their 65-hour journeys to the Moon. Highlighted in this image is the camera tower of the Ranger spacecraft.

On July 28, 1964, Ranger 7 was launched from Cape Canaveral, Florida. Like Ranger 6, the spacecraft was first put into Earth orbit before being boosted on a lunar trajectory. The launch system and the spacecraft seemed to operate flawlessly. Still, between launch and arrival at the Moon, Ranger’s engineers and scientists got little sleep. Rangers 1-6 had taught them that problems could arise all the way up to the last second. Finally, on July 31, Ranger 7 reached the Moon. During its final 17 minutes of flight, the spacecraft sent back 4,308 images of the lunar surface. The last image taken before impact had a resolution of just half-a-meter. The area in which it crashed – between Mare Nubium and Oceanus Procellarum – was named Mare Cognitum, Latin for “The Sea that has Become Known,” in honor of being the first spot on the Moon seen close-up.

Ranger 7 took this image, the first picture of the Moon by a U.S. spacecraft, on July 31, 1964.

Ranger 7 took this image, the first picture of the Moon by a U.S. spacecraft, on July 31, 1964. Credit: NASA

Two more Ranger missions followed. Ranger 8 returned more than 7,000 images of the Moon. And Ranger 9 returned “live” TV images of the Alphonsus crater and the surrounding area as it approached its crash site in the crater—letting millions of Americans see the Moon up-close like never before.