page_title: Apollo 15
section_title: Lunar orbit and landing
hierarchical_section_title: Apollo 15 / Mission highlights / Lunar orbit and landing
caption_attribution_description: English: A large group of photographs showing the interior of the Apollo 15 Lunar Module (LM) showing controls and panels. KSC, Cape Kennedy, Florida. Image ID: S71-40761 Polski: Fotografia wnętrza modułu księżycowego przed misją Apollo 15 ukazuje panele sterowania. KSC, Przylądek Kennedyego, Floryda. Image ID: S71-40761. Ta fotografia posiada objaśnienia i jeżeli one nie wyświetlają się, należy kliknąć odsyłacz: Zobacz objaśnienia na commons
context_page_description: Apollo 15 was the ninth crewed mission in the United States' Apollo program, and the fourth to land on the Moon. It was the first J mission, with a longer stay on the Moon and a greater focus on science than earlier landings. Apollo 15 saw the first use of the Lunar Roving Vehicle.
  The mission began on July 26, 1971, and ended on August 7, the lunar surface exploration taking place between July 30 and August 2. Commander David Scott and Lunar Module Pilot James Irwin landed near Hadley Rille and explored the local area using the rover, allowing them to travel further from the lunar module than had been possible on previous missions. They spent 18​¹⁄₂ hours on the Moon's surface on extravehicular activity, and collected 170 pounds of surface material.
  At the same time, Command Module Pilot Alfred Worden orbited the Moon, operating the sensors in the SIM bay of the service module. This suite of instruments collected data on the Moon and its environment using a panoramic camera, a gamma-ray spectrometer, a mapping camera, a laser altimeter, a mass spectrometer, and a lunar subsatellite deployed at the end of the moonwalks.
context_section_description: On Apollo 11 and 12, the lunar module decoupled from the CSM and descended to a much lower orbit from which the lunar landing attempt commenced; to save fuel in an increasingly heavy lander, beginning with Apollo 14, the SPS in the service module made that burn, known as descent orbit insertion (DOI), with the lunar module still attached to the CSM. The initial orbit Apollo 15 was in had its apocynthion, or high point, over the landing site at Hadley; a burn at the opposite point in the orbit was performed, with the result that Hadley would now be under the craft's pericynthion, or low point. The DOI burn was performed at 082:39:49.09 and took 24.53 seconds; the result was an orbit with apocynthion of 58.5 nautical miles (108.3 km; 67.3 mi) and pericynthion of 9.6 nautical miles (17.8 km; 11.0 mi). Overnight between July 29 and 30, as the crew rested, it became apparent to Mission Control that mass concentrations in the Moon were making Apollo 15's orbit increasingly elliptical—pericynthion was 7.6 nautical miles (14.1 km; 8.7 mi) by the time the crew was awakened on July 30. This, and uncertainty as to the exact altitude of the landing site, made it desirable that the orbit be modified, or trimmed. Using the craft's RCS thrusters, this took place at 095:56:44.70, lasting 30.40 seconds, and raised the pericynthion to 8.8 nautical miles (16.3 km; 10.1 mi) and the apocynthion to 60.2 nautical miles (111.5 km; 69.3 mi).
  As well as preparing the lunar module for its descent, the crew continued observations of the Moon (including of the landing site at Hadley) and provided television footage of the surface. Then, Scott and Irwin entered the lunar module in preparation for the landing attempt. Undocking was planned for 100:13:56, over the far side of the Moon, but nothing happened when separation was attempted. After analyzing the problem, the crew and Houston decided the probe instrumentation umbilical was likely loose or disconnected; Worden went into the tunnel connecting the command and lunar modules and determined this was so, seating it more firmly. With the problem resolved, Falcon separated from Endeavour at 100:39:16.2, about 25 minutes late, at an altitude of 5.8 nautical miles (10.7 km; 6.7 mi). Worden in Endeavour executed a SPS burn at 101:38:58.98 to send Endeavour to an orbit of 65.2 nautical miles (120.8 km; 75.0 mi) by 54.8 nautical miles (101.5 km; 63.1 mi) in preparation for his scientific work.
  Aboard Falcon, Scott and Irwin prepared for powered descent initiation (PDI), the burn that was to place them on the lunar surface, and, after Mission Control gave them permission, they initiated PDI at 104:30:09.4 at an altitude of 5.8 nautical miles (10.7 km; 6.7 mi), slightly higher than planned. During the first part of the descent, Falcon was aligned so the astronauts were on their backs and thus could not see the lunar surface below them, but after the craft made a pitchover maneuver, they were upright and could see the surface in front of them. Scott, who as commander performed the landing, was confronted with a landscape that did not at first seem to resemble what he had seen during simulations. Part of this was due to an error in the landing path of some 3,000 feet (910 m), of which CAPCOM Ed Mitchell informed the crew prior to pitchover; part because the craters Scott had relied on in the simulator were difficult to make out under lunar conditions, and he initially could not see Hadley Rille. He concluded that they were likely to overshoot the planned landing site, and, once he could see the rille, started maneuvering the vehicle to move the computer's landing target back towards the planned spot, and looked for a relatively smooth place to land.
  Below about 60 feet (18 m), Scott could see nothing of the surface because of the quantities of lunar dust being displaced by Falcon's exhaust. Falcon had a larger engine bell than previous LMs, in part to accommodate a heavier load, and the importance of shutting down the engine at initial contact rather than risk "blowback", the exhaust reflecting off the lunar s
caption: The interior of Falcon
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