Apollo 15 lunar surface operations were conducted from July 30 to August 2, 1971, by Apollo 15 Commander David Scott and Apollo Lunar Module Pilot James Irwin, who used the first Lunar Roving Vehicle to make three exploratory trips away from their landing site at the base of the Apennine Mountains, near Hadley Rille.
They collected a total of of lunar surface material during 18½ hours outside the Lunar Module Falcon.
Landing At 104 hours, 30 minutes and 12 seconds GET the descent engine of Falcon ignited. Burning at about 10% for the first 26 seconds so that the guidance computer could gimbal the engine to direct the thrust through the center of gravity of the LM, it then thrust up to 100%. Irwin confirmed that the Abort Guidance System (AGS) agreed with the Primary Guidance and Navigation System (PGNS) on their height and rate of descent.
At three minutes the computer rolled the spacecraft so that they were now on their back, with the windows facing away from the lunar surface. This was so the landing radar could acquire the surface. Scott then announced the altitude and velocity lights, indicating the computer was getting acceptable data from the radar. Six minutes into the burn they were 30,000 feet (9000 m) above the surface.
In Mission Control, the Flight Director learned that tracking data indicated they were going to land 3000 feet (900 m) south of the targeted landing site. Although at first he decided not to tell the crew, Ed Mitchell, the CapCom, convinced him otherwise. During this time Scott was trying to see the ground through his window. He thought they were going to land as long as he could see Mount Hadley Delta. He was unable to see the Rille, something that had been possible in the simulators.
Nine minutes and ten seconds into the burn, Program 64 started on the computer and the LM pitched forward and the crew could see the ground. Using scribe marks on the window and angles read to him by Irwin, Scott found where the computer was predicting the landing site to be and then used a hand controller to move the predicted location. He did this 18 times during the landing, moving the target site a total of 338 meters (1110 feet) uprange and 409 meters (1341 feet) north.
Scott's main problem was that there was very little detail on the surface. The best images of the site only had 66 ft (20 m) resolution and photoanalysers had overenhanced the images. The main problem was overestimating the depth of craters, so as to make them have shadows at higher sun angles. Fortunately he was able to see four craters, Matthew, Mark, Luke and Index (the reason it was called Index and not John was due to Madalyn Murray O'Hair, an outspoken atheist who had sued NASA over the reading of Genesis during Apollo 8. Although she lost the case, NASA remained squeamish on overtly religious announcements on later flights).
Irwin began reading the altitude, rate of descent and the projected landing site. At 400 ft (120 m), the computer was switched to Program 66, designed for the landing phase. From now on Scott was flying manually. Irwin stopped reading out the projected landing site. Passing through 120 ft (37 m) Scott said he was picking up some dust. By the time they got to between 60 and 50 ft (18 to 15 m) the view outside would be completely obscured by dust.
Irwin then announced that the contact light had illuminated, indicating one of the landing probes on the LM's feet had contacted the ground. Immediately Scott cut the engine. With the extended engine bell there was a fear that it could touch the ground and cause exhaust to travel back into the engine. It is estimated that they were travelling 6.8 ft/s (2 m/s) when they hit, twice as fast as previous missions. A few seconds later, Scott informed the ground that "Okay, Houston. The Falcon is on the Plain at Hadley." Falcon was tilted nearly 10 degrees to its back left, just 5° below the maximum acceptable angle. It set down on the rim of a crater such that its engine bell was damaged, and with one of the legs in the crater. They were about 600 meters north and about 175 meters west of the targeted landing site. This was of little concern though thanks to the capabilities of the rover.
Stand-up EVA
Before they ventured outside for the first time, Scott and Irwin would sleep. Both had realized that in order to be at their best for their seven-hour Extra-vehicular activity they would need to be rested. But Scott had also learned the need to get an overview of a new survey site before venturing outside. As such he convinced mission planners to let them conduct a stand-up EVA before the first sleep period. It also gave them a stable platform to use a 500 mm telephoto lens that was carried on this mission for the first time. The lens had been a struggle to get on board a spacecraft where weight savings were measured in pounds.
Two hours after landing, they depressurized the LM and removed the top hatch and docking mechanism. Then, Scott stood on top of the ascent engine cover and put his head outside. Looking around, Scott was familiar with the territory having spent months studying maps of the area. He could easily recognize Mons Hadley, Mons Hadley Delta, the Swan Range, the Silver Spur, Bennett Hill, Hill 305, and the North Complex.
Scott's first task was to take a 22-picture stereo panorama of the area using a 60 mm lens. Then he photographed targets of interest with the telephoto lens, and then a color panorama of the area with the 60 mm lens.
He was able to put to bed any further concerns about the use of the Rover. Radar observations from Earth had given the impression that the area was covered in large boulders that would make it impossible to traverse with the Rover. Scott saw that there was nothing bigger than 6 to 8 inches (15 to 20 cm) near them. He then described the features he could see around him. Basically this was to give a general setting of the area and make sure there were no great surprises. Thirty minutes after opening the hatch, Scott re-entered and the hatch was closed and Falcon repressurized.
EVA-1
Throughout the astronauts' sleep period, Mission Control had watched with some concern as the pressure inside descent stage oxygen tanks of the LM slowly dropped. To conserve power during the night, the LM was run on a low-data-rate telemetry stream, so Mission Control could not tell the exact cause. Unwilling to wake the crew they decided to wait until they had woken up.
In the end, Flight Director Peter Frank chose to wake the crewmen an hour early and got them to turn back on the high-data-rate telemetry. With this they saw that the valve of the Urine Transfer Device was open even though the receptacle was capped. A total of about 8 out of 95 pounds (3.6 out of 43 kg) of oxygen had been lost. About half of the total amount was reserve. Scott and Irwin would state in the post-flight Technical Debrief that Mission Control should have awakened them as soon as the leak was detected.
Once they were awake, it was decided to start their preparations for the first lunar EVA of their mission. As with everything in Apollo, it was an involved procedure. Not only did they have to prepare Falcon, but had to don their space suits. Apollo 15 was the first crew that got to sleep in long johns rather than having to stay in their space suits. It would not be until four hours after waking up that Mission Control gave the Go to depressurize the LM.
As Scott became the seventh man to step onto the lunar surface, he said:
As I stand out here in the wonders of the unknown at Hadley, I sort of realize there's a fundamental truth to our nature. Man must explore. And this is exploration at its greatest.
After inspecting the LM, Scott began to unpack the Modularised Equipment Stowage Assembly (MESA), which was attached to the side of the LM and carried the Apollo TV camera, sample bags, batteries, CO2 scrubbers for the space suits, and other equipment needed while the astronauts were outside the spacecraft. About seven minutes after Scott stepped outside Irwin was on the surface.
Irwin's first task was to collect a contingency sample of lunar rock. This was collected in case of an emergency, i.e., suddenly having to leave the lunar surface within the first few minutes. In such an event having a contingency sample meant that the crew would not return to Earth empty-handed. However, the contingency sample was not of much value because the ground surrounding the landing site had been disturbed by the LM descent engine.
After Scott positioned the TV camera on a tripod so Mission Control could see the deployment of the Lunar Rover, he and Irwin began the process by pulling on two lanyards. These released the Rover and let it swing down on hinges. As it did, it began to unfold. They experienced some problems at first due to the angle the LM was sitting on, but within minutes it was on the ground almost ready to go.
Scott had the honor of the first test drive, taking it around the LM. The Rover had both front and back steering, but Scott found that only the rear-wheel steering was working (mysteriously the front steering would be working at the start of the second EVA). Other difficulties came from how their space suits did not bend very much when they sat down. When training on Earth, their body weight had forced the suits down, but on the Moon, they ended up reclining in the seats. Also their bouncing up and down on the seats during the traverses (as a result of the rough terrain) resulted in the adding of seat belts for the LRV's on Apollos 16 and 17. Apart from the steering there were no other problems and the crew set about loading up the Rover for their first geological traverse. During lunar surface operations, Commander Scott always drove the rover, while Lunar Module Pilot Irwin was a passenger who assisted with navigation. This division of responsibilities between the two crew positions was used consistently throughout Apollo's J missions.
The astronauts could not travel any farther than the distance they could walk with the remaining oxygen in their Portable Life Support Systems (PLSS). So the earlier they set out, the farther they could travel. They would travel to the farthest point of the traverse and then work their way back. On EVA-1 they would travel to the base of Hadley Delta via the Rille. Their first target (Station 1) was the crater dubbed Elbow crater, so-called as it sat at a bend in the Rille. The first EVA also served an important task of working out exactly where they had landed. The Rover carried a navigation system that could calculate the distance and direction of a known starting point. By travelling to a known point this could be calibrated.
Scott set off at 9 km/h (6 mph), slow by terrestrial standards, but due to the lowness of the chassis of the Rover and the roughness of the surface, the astronauts would say it seemed quite quick. Throughout the journey, the astronauts had trouble identifying where they were. Due to not knowing exactly where the landing site was and over-enhanced maps, little was familiar. But the route chosen for this first drive had been picked with this in mind. By driving along the side of the rille it would be hard to miss their target.
After arriving at Elbow, Irwin's first task was to take a panorama of the site. At the same time Scott aligned the S-band antenna of the Rover with the Earth. This allowed Mission Control to operate the TV camera. Ed Fendell was in charge of controlling the camera and took his own pan so geologists in the backroom could see the site. The backroom kept track of everything that astronauts did on geology. As a sample was collected they would note its number, location and description on a card.