Editing Apollo 17 (section)

== Mission hardware and experiments ==
[[File:Apollo 17 The Last Moon Shot Edit1.jpg|thumb|upright=1.3|SA-512, Apollo 17's Saturn V rocket, on the launch pad awaiting liftoff, November 1972|alt=Saturn five rocket on a launch pat at dusk while cloudy outside.]]

=== Spacecraft and launch vehicle ===
The Apollo 17 spacecraft comprised CSM-114 (consisting of Command Module 114 (CM-114) and Service Module 114 (SM-114)); Lunar Module 12 (LM-12);{{sfn|Orloff & Harland 2006|p=508}} a Spacecraft-Lunar Module Adapter (SLA) numbered SLA-21; and a Launch Escape System (LES).{{sfn|Apollo 17 Press Kit|pp=97–99}}<ref name="hardware">{{cite web|title=Apollo/Skylab ASTP and Shuttle Orbiter Major End Items|date=March 1978|url=https://s3.documentcloud.org/documents/6473665/Apollo-Skylab-ASTP-and-Shuttle-Orbiter-Major-End.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://s3.documentcloud.org/documents/6473665/Apollo-Skylab-ASTP-and-Shuttle-Orbiter-Major-End.pdf |archive-date=2022-10-09 |url-status=live|publisher=NASA|page=15}}</ref> The LES contained a rocket motor that would propel the CM to safety in the event of an aborted mission in the moments after launch, while the SLA housed the LM during the launch and early part of the flight. The LES was jettisoned after the launch vehicle ascended to the point that it was not needed, while the SLA was left atop the [[S-IVB]] third stage of the rocket after the CSM and LM separated from it.{{sfn|Apollo 17 Press Kit|p=97}}{{sfn|Orloff & Harland 2006|p=26}}

The launch vehicle, SA-512,{{sfn|Orloff & Harland 2006|p=508}} was one of fifteen [[Saturn V]] rockets built,<ref>{{cite news |last1=Sharp |first1=Tim |title=Saturn V Rockets & Apollo Spacecraft |url=https://www.space.com/16698-apollo-spacecraft.html |access-date=February 7, 2022 |publisher=Space.com |date=October 17, 2018 |archive-date=February 11, 2022 |archive-url=https://web.archive.org/web/20220211052532/https://www.space.com/16698-apollo-spacecraft.html |url-status=live }}</ref> and was the twelfth to fly.<ref>{{cite web|publisher=[[NASA]]|title=Saturn V|work=Rocket Park|url=https://www.nasa.gov/centers/johnson/rocketpark/saturn_v.html|access-date=February 8, 2022|archive-date=April 8, 2015|archive-url=https://web.archive.org/web/20150408004131/https://www.nasa.gov/centers/johnson/rocketpark/saturn_v.html|url-status=dead}}</ref> With a weight at launch of {{convert|6529784|lb}} ({{convert|116269|lb}} of which was attributable to the spacecraft), Apollo 17's vehicle was slightly lighter than Apollo 16, but heavier than every other crewed Apollo mission.{{sfn|Orloff & Harland 2006|pp=584–585}}

====Preparation and assembly====
The first piece of the launch vehicle to arrive at [[Kennedy Space Center]] was the [[S-II]] second stage, on October 27, 1970; it was followed by the S-IVB on December 21; the [[S-IC]] first stage did not arrive until May 11, 1972, followed by the Instrument Unit on June 7. By then, LM-12 had arrived, the ascent stage on June 16, 1971, and the descent stage the following day; they were not mated until May 18, 1972. CM-114, SM-114 and SLA-21 all arrived on March 24, 1972. The rover reached Kennedy Space Center on June 2, 1972.{{sfn|Orloff & Harland 2006|p=512}}

[[File:Apollo 17 Astronaut Training - GPN-2000-000640.jpg|thumb|upright=1.3|Cernan (seated, right) and Schmitt in the training [[Lunar Roving Vehicle]], with the mockup [[Lunar Module]] in the background, August 1972|alt=Schmitt, (left), Cernan, (right) in a training LRV, with the Lunar Landing Module in the background.]]
The CM and the service module (SM) were mated on March 28, 1972,{{sfn|Orloff & Harland 2006|p=512}} and the testing of the spacecraft began that month.<ref name="moonport"/> The CSM was placed in a vacuum chamber at Kennedy Space Center, and the testing was conducted under those conditions. The LM was also placed in a vacuum chamber; both the prime and the backup crews participated in testing the CSM and LM.{{sfn|Apollo 17 Press Kit|p=15}} During the testing, it was discovered that the LM's rendezvous radar assembly had received too much voltage during earlier tests; it was replaced by the manufacturer, [[Grumman]]. The LM's landing radar also malfunctioned intermittently and was also replaced. The front and rear steering motors of the [[Lunar Roving Vehicle]] (LRV) also had to be replaced, and it required several modifications.<ref name="moonport">{{cite book |last1=Benson |first1=Charles D. |last2=Faherty |first2=William Barnaby |title=Moonport: A History of Apollo Launch Facilities and Operations |url=https://www.hq.nasa.gov/office/pao/History/SP-4204/contents.html |access-date=November 23, 2021 |year=1978 |publisher=NASA |id=NASA SP-4204 |chapter=Ch. 23-7: The Apollo-Saturn IB Space Vehicle |chapter-url=https://www.hq.nasa.gov/office/pao/History/SP-4204/ch23-7.html |archive-date=January 23, 2008 |archive-url=https://web.archive.org/web/20080123133438/https://www.hq.nasa.gov/office/pao/History/SP-4204/contents.html |url-status=dead }}</ref> Following the July 1972 removal from the vacuum chamber, the LM's landing gear was installed, and it, the CSM and the SLA were mated to each other. The combined craft was moved into the [[Vehicle Assembly Building]] in August for further testing, after which it was mounted on the launch vehicle.{{sfn|Apollo 17 Press Kit|p=15}} After completing testing, including a simulated mission, the LRV was placed in the LM on August 13.{{sfn|Apollo 17 Press Kit|p=16}}

Erection of the stages of the launch vehicle began on May 15, 1972, in High Bay 3 of the Vehicle Assembly Building, and was completed on June 27. Since the launch vehicles for [[Skylab 1]] and [[Skylab 2]] were being processed in that building at the same time, this marked the first time NASA had three launch vehicles there since the height of the Apollo program in 1969. After the spacecraft was mounted on the launch vehicle on August 24,{{sfn|Apollo 17 Press Kit|p=16}} it was rolled out to Pad 39-A on August 28.{{sfn|Orloff & Harland 2006|p=512}} Although this was not the final time a Saturn V would fly (another would lift [[Skylab]] to orbit), area residents reacted as though it was, and 5,000 of them watched the rollout, during which the prime crew joined the operating crew from [[Bendix Corporation|Bendix]] atop the crawler.<ref name="moonport"/>

At Pad 39-A, testing continued, and the CSM was electrically mated to the launch vehicle on October 11, 1972. Testing concluded with the countdown demonstration tests, accomplished on November 20 and 21.{{sfn|Orloff & Harland 2006|p=512}} The countdown to launch began at 7:53&nbsp;a.m. (12:53 UTC) on December 5, 1972.{{sfn|Orloff & Harland 2006|p=510}}

===Lunar surface science===

==== ALSEP ====
The [[Apollo Lunar Surface Experiments Package]] was a suite of nuclear-powered experiments, flown on each landing mission after Apollo 11. This equipment was to be emplaced by the astronauts to continue functioning after the astronauts returned to Earth.{{sfn|Orloff & Harland 2006|pp=601–602}} For Apollo 17, the ALSEP experiments were a [[Heat Flow Experiment]] (HFE), to measure the rate of heat flow from the interior of the Moon, a [[Lunar Surface Gravimeter]] (LSG), to measure alterations in the lunar gravity field at the site,{{sfn|Orloff 2004|loc=Statistical Tables: Lunar Surface Experiments}} a [[Lunar Atmospheric Composition Experiment]] (LACE), to investigate what the lunar atmosphere is made up of,<ref name="lace">{{cite web |title=Science Experiments – Lunar Atmospheric Composition |url=https://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/experiments/lace/#:~:text=The%20Lunar%20Atmospheric%20Composition%20Experiment,by%20the%20Cold%20Cathode%20Gauge. |publisher=Lunar and Planetary Institute |access-date=February 8, 2022 |archive-date=July 9, 2021 |archive-url=https://web.archive.org/web/20210709143320/https://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/experiments/lace/#:~:text=The%20Lunar%20Atmospheric%20Composition%20Experiment,by%20the%20Cold%20Cathode%20Gauge. |url-status=live }}</ref> a [[Lunar Seismic Profiling Experiment]] (LSPE), to detect nearby seismic activity, and a [[Lunar Ejecta and Meteorites Experiment]] (LEME), to measure the velocity and energy of dust particles.{{sfn|Orloff 2004|loc=Statistical Tables: Lunar Surface Experiments}} Of these, only the HFE had been flown before; the others were new.{{sfn|Orloff & Harland 2006|pp=601–602}}

The HFE had been flown on the aborted Apollo 13 mission, as well as on Apollo 15 and 16, but placed successfully only on Apollo 15, and unexpected results from that device made scientists anxious for a second successful emplacement. It was successfully deployed on Apollo 17.{{sfn|Chaikin 1995|pp=467–469, 478, 513}} The lunar gravimeter was intended to detect wavers in gravity, which would provide support for [[Albert Einstein]]'s [[general theory of relativity]];<ref>{{cite news |last1=Lunsford |first1=Christine |title=Apollo 17: NASA's Last Apollo Moon Landing Mission in Pictures |url=https://www.space.com/39006-apollo-17-moon-landing-mission-photos/2.html |access-date=February 8, 2022 |publisher=Space.com |date=December 7, 2017 |archive-date=February 8, 2022 |archive-url=https://web.archive.org/web/20220208025314/https://www.space.com/39006-apollo-17-moon-landing-mission-photos/2.html |url-status=live }}</ref> it ultimately failed to function as intended.<ref name="alsjtge"/> The LACE was a surface-deployed module that used a [[mass spectrometer]] to analyze the Moon's atmosphere.<ref>{{cite report |last1=Stern |first1=S. Alan |title=The Lunar Atmosphere: History, Status, Current Problems, and Context |year=1999 |publisher=Southwest Research Institute |citeseerx=10.1.1.21.9994 }}</ref> On previous missions, the [[Cold Cathode Gauge Experiment|Code Cathode Gauge]] experiment had measured the quantity of atmospheric particles, but the LACE determined which gases were present: principally neon, helium and hydrogen.<ref name="lace"/> The LSPE was a seismic-detecting device that used [[geophone]]s, which would detect explosives to be set off by ground command once the astronauts left the Moon.{{sfn|Orloff 2004|loc=Statistical Tables: Lunar Surface Experiments}} When operating, it could only send useful data to Earth in high bit rate, meaning that no other ALSEP experiment could send data then, and limiting its operating time. It was turned on to detect the liftoff of the ascent stage, as well as use of the explosives packages, and the ascent stage's impact, and thereafter about once a week, as well as for some 100 hour periods.<ref>{{cite web |title=Lunar Seismic Profiling Experiment |url=https://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/experiments/lspe/Apollo-17-active-seismic-NSSDCA.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/experiments/lspe/Apollo-17-active-seismic-NSSDCA.pdf |archive-date=2022-10-09 |url-status=live|publisher=Lunar and Planetary Institute}}</ref> The LEME had a set of detectors to measure the characteristics of the dust particles it sought.{{sfn|Orloff 2004|loc=Statistical Tables: Lunar Surface Experiments}} It was hoped that the LEME would detect dust impacting the Moon from elsewhere, such as from comets or interstellar space, but analysis showed that it primarily detected dust moving at slow speeds across the lunar surface.<ref name="leme">{{cite web |title=Science Experiments – Lunar Ejecta and Meteorite |url=https://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/experiments/lem/ |publisher=Lunar and Planetary Institute |access-date=February 12, 2022 |archive-date=January 20, 2022 |archive-url=https://web.archive.org/web/20220120031105/https://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/experiments/lem/ |url-status=live }}</ref>

All powered ALSEP experiments that remained active were deactivated on September 30, 1977,{{sfn|Orloff & Harland 2006|pp=601–602}} principally because of budgetary constraints.<ref name="astro">{{cite news|newspaper=[[Astronomy (magazine)|Astronomy]]|access-date=February 1, 2021|title=What did the Apollo astronauts leave behind?|date=June 21, 2019|last=Talcott|first=Richard|url=https://astronomy.com/news/2019/06/what-did-the-apollo-astronauts-leave-behind|archive-date=February 1, 2022|archive-url=https://web.archive.org/web/20220201050005/https://astronomy.com/news/2019/06/what-did-the-apollo-astronauts-leave-behind|url-status=live}}</ref>

==== Other lunar-surface science ====
[[File:Apollo 17 rover at final resting site.jpg|thumb|Apollo 17's [[Lunar Roving Vehicle]]. The Surface Electrical Properties (SEP) experiment receiver is the antenna on the right-rear of the vehicle|alt=Black and white photo of a lunar rover with a lunar landing module in the background.]]Like Apollo 15 and 16, Apollo 17 carried a Lunar Roving Vehicle. In addition to being used by the astronauts for transport from station to station on the mission's three moonwalks, the LRV was used to transport the astronauts' tools, communications equipment, and the lunar samples they gathered.<ref name="lunarrover">{{cite web |title=Lunar Roving Vehicle (LRV) |url=https://airandspace.si.edu/explore-and-learn/topics/apollo/apollo-program/spacecraft/lrv.cfm |website=The Apollo Program |publisher=National Air and Space Museum |access-date=February 8, 2022 |archive-date=February 8, 2022 |archive-url=https://web.archive.org/web/20220208032714/https://airandspace.si.edu/explore-and-learn/topics/apollo/apollo-program/spacecraft/lrv.cfm |url-status=dead }}</ref> The Apollo 17 LRV was also used to carry some of the scientific instruments, such as the [[Lunar Traverse Gravimeter|Traverse Gravimeter Experiment (TGE)]] and Surface Electrical Properties (SEP) experiment.<ref name="alsjtge" /><ref name="sep">{{cite web|title=Science Experiments – Surface Electrical Properties|url=http://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/experiments/sep/|work=Apollo 17 Mission|publisher=Lunar and Planetary Institute|access-date=February 7, 2022|archive-date=October 3, 2011|archive-url=https://web.archive.org/web/20111003195214/http://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/experiments/sep/|url-status=live}}</ref> The Apollo 17 LRV traveled a cumulative distance of approximately {{convert|35.7|km|mi nmi|abbr=on}} in a total drive time of about four hours and twenty-six minutes; the greatest distance Cernan and Schmitt traveled from the lunar module was about {{convert|7.6|km|mi nmi|abbr=on}}.{{sfn|Orloff 2004|loc=Statistical Tables: Extravehicular Activity}}

This was the only mission to carry the TGE, which was built by [[Draper Laboratory]] at the [[Massachusetts Institute of Technology]]. As gravimeters had been useful in studying the Earth's internal structure, the objective of this experiment was to do the same on the Moon. The gravimeter was used to obtain relative gravity measurements at the landing site in the immediate vicinity of the lunar module, as well as various locations on the mission's traverse routes. Scientists would then use this data to help determine the geological substructure of the landing site and the surrounding vicinity. Measurements were taken while the TGE was mounted on the LRV, and also while the device was placed on the lunar surface. A total of 26 measurements were taken with the TGE during the mission's three moonwalks, with productive results.<ref name="alsjtge">{{cite web|url=http://www.hq.nasa.gov/alsj/a17/a17-TGE.html|title=Apollo 17 Traverse Gravimeter Experiment|publisher=NASA|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 17 Lunar Surface Journal|access-date=November 29, 2021|archive-date=September 7, 2011|archive-url=https://web.archive.org/web/20110907121516/http://www.hq.nasa.gov/alsj/a17/a17-TGE.html|url-status=live}}</ref>

The SEP was also unique to Apollo 17, and included two major components: a transmitting antenna deployed near the lunar module and a receiver mounted on the LRV. At different stops during the mission's traverses, electrical signals traveled from the transmitting device, through the ground, and were received at the LRV. The electrical properties of the [[lunar regolith]] could be determined by comparison of the transmitted and received electrical signals. The results of this experiment, which are consistent with [[Moon rock|lunar rock]] composition, show that there is almost no water in the area of the Moon in which Apollo 17 landed, to a depth of {{convert|2|km|mi nmi|abbr=on}}.<ref name="sep" />

A {{convert|2.4|meter|feet|abbr=on}} long, {{convert|2|cm|inch|abbr=on}} diameter{{sfn|Apollo 17 Press Kit|p=46}} device, the Lunar Neutron Probe was inserted into one of the holes drilled into the surface to collect core samples. It was designed to measure the quantity of neutrons which penetrated to the detectors it bore along its length. This was intended to measure the rate of the "gardening" process on the lunar surface, whereby the regolith on the surface is slowly mixed or buried due to micrometeorites and other events. Placed during the first EVA, it was retrieved during the third and final EVA. The astronauts brought it with them back to Earth, and the measurements from it were compared with the evidence of neutron flux in the core that had been removed from the hole it had been placed in. Results from the probe and from the cores were instrumental in current theories that the top centimeter of lunar regolith turns over every million years, whereas "gardening" to a depth of one meter takes about a billion years.<ref name ="probe">{{cite web|publisher=[[Lunar and Planetary Institute]]|work=Apollo 17 Mission|title=Science Experiments – Lunar Neutron Probe|date=2019|access-date=February 12, 2022|url=https://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/experiments/lnp/|archive-date=September 8, 2021|archive-url=https://web.archive.org/web/20210908125848/https://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/experiments/lnp/|url-status=live}}</ref>

===Orbital science===

==== Biological experiments ====
{{Main|Fe, Fi, Fo, Fum, and Phooey}}

Apollo 17's CM carried a biological cosmic ray experiment (BIOCORE), containing five mice that had been implanted with radiation monitors under their scalps to see whether they suffered damage from cosmic rays. These animals were placed in individual metal tubes inside a sealed container that had its own oxygen supply, and flown on the mission. All five were pocket mice (''[[Perognathus longimembris]]'');{{sfn|Johnson et al. 1975|loc=Ch. 4}} this species was chosen because it was well-documented, small, easy to maintain in an isolated state (not requiring drinking water during the mission and with highly concentrated waste), and for its ability to withstand environmental stress.{{sfn|Apollo 17 Preliminary Science Report|pp=26-1–26-14}} Officially, the mice—four male and one female—were assigned the identification numbers A3326, A3400, A3305, A3356 and A3352. Unofficially, according to Cernan, the Apollo 17 crew dubbed them Fe, Fi, Fo, Fum, and Phooey.{{sfn|Burgess & Dubbs 2007|p=320}}

Four of the five mice survived the flight, though only two of them appeared healthy and active; the cause of death of the fifth mouse was not determined. Of those that survived, the study found [[lesion]]s in the scalp itself and, in one case, the liver. The scalp lesions and liver lesions appeared to be unrelated to one another; nothing was found that could be attributed to cosmic rays.{{sfn|Johnson et al. 1975|loc=Part IV, Ch. 4}}

The Biostack experiment was similar to one carried on Apollo 16, and was designed to test the effects of the cosmic rays encountered in space travel on microorganisms that were included, on seeds, and on the eggs of simple animals ([[brine shrimp]] and beetles), which were carried in a sealed container. After the mission, the microorganisms and seeds showed little effect, but many of the eggs of all species failed to hatch, or to mature normally; many died or displayed abnormalities.{{sfn|Johnson et al. 1975|loc=Part IV, Ch. 1}}

==== Scientific Instrument Module ====
[[File:Apollo 17 CSM SIM bay.jpg|thumb|upright=1.2|right|Apollo 17 SIM bay on the service module ''America'', seen from the Lunar Module ''Challenger'' in orbit around the Moon]]

The Apollo 17 SM contained the scientific instrument module (SIM) bay. The SIM bay housed three new experiments for use in lunar orbit: a lunar sounder, an [[infrared]] scanning [[radiometer]], and a [[Ultraviolet|far-ultraviolet]] spectrometer. A mapping camera, panoramic camera, and a [[Lidar|laser altimeter]], which had been carried previously, were also included in the SIM bay.<ref name ="science">{{cite web |title=Apollo 17 – Lunar Science |url=https://airandspace.si.edu/explore-and-learn/topics/apollo/apollo-program/landing-missions/apollo17-science.cfm |website=The Apollo Program |publisher=National Air and Space Museum |access-date=February 8, 2022 |archive-date=February 8, 2022 |archive-url=https://web.archive.org/web/20220208021215/https://airandspace.si.edu/explore-and-learn/topics/apollo/apollo-program/landing-missions/apollo17-science.cfm |url-status=dead }}</ref>

The lunar sounder was to beam [[Electromagnetic radiation|electromagnetic]] impulses toward the lunar surface, which were designed with the objective of obtaining data to assist in developing a geological model of the interior of the Moon to an approximate depth of {{convert|1.3|km|mi|abbr=on}}.<ref name="science"/> The infrared scanning radiometer was designed with the objective of generating a temperature map of the lunar surface to aid in locating surface features such as rock fields, structural differences in the [[Internal structure of the Moon|lunar crust]], and volcanic activity. The far-ultraviolet spectrometer was to be used to obtain information on the composition, density, and constituency of the [[Atmosphere of the Moon|lunar atmosphere]]. The spectrometer was also designed to detect far-UV radiation emitted by the Sun that had been reflected off the lunar surface. The laser altimeter was designed to measure the altitude of the spacecraft above the lunar surface within approximately {{convert|2|m|ft|abbr=off|sp=us}}, providing altitude information to the panoramic and mapping cameras, which were also in the SIM bay.<ref name="science"/>{{sfn|Apollo 17 Press Kit|pp=56–59}}

==== Light-flash phenomenon and other experiments ====
{{main|Cosmic ray visual phenomena}}

Beginning with Apollo 11, crew members observed light flashes that penetrated their closed eyelids. These flashes, described by the astronauts as "streaks" or "specks" of light, were usually observed while the spacecraft was darkened during a sleep period. These flashes, while not observed on the lunar surface, would average about two per minute and were observed by the crew members during the trip out to the Moon, back to Earth, and in lunar orbit.<ref name="lightflash"/>

The Apollo 17 crew repeated an experiment, also conducted on Apollo 16, with the objective of linking these light flashes with [[cosmic ray]]s. Evans wore a device over his eyes that recorded the time, strength, and path of high-energy atomic particles that penetrated the device, while the other two wore blindfolds to keep out light. Investigators concluded that the available evidence supports the hypothesis that these flashes occur when charged particles travel through the [[retina]] in the eye.<ref name=lightflash>{{cite book |last1=Osborne |first1=W. Zachary |last2=Pinsky |first2=Lawrence S. |last3=Bailey |first3=J. Vernon |editor-last1=Johnston |editor-first1=Richard S. |editor-last2=Dietlein |editor-first2=Lawrence F. |editor-last3=Berry |editor-first3=Charles A. |others=Foreword by [[Christopher C. Kraft Jr.]] |title=Biomedical Results of Apollo |url=http://lsda.jsc.nasa.gov/books/apollo/cover.htm |access-date=August 26, 2011 |year=1975 |publisher=NASA |location=Washington, D.C. |id=NASA SP-368 |chapter=Apollo Light Flash Investigations |chapter-url=http://lsda.jsc.nasa.gov/books/apollo/S4CH2.htm |url-status=dead |archive-url=https://web.archive.org/web/20110917234433/http://lsda.jsc.nasa.gov/books/apollo/cover.htm |archive-date=September 17, 2011 }}</ref>

Apollo 17 carried a sodium-iodide crystal identical to the ones in the gamma-ray spectrometer flown on Apollo 15 and 16. Data from this, once it was examined on Earth, was to be used to help form a baseline, allowing for subtraction of rays from the CM or from [[cosmic radiation]] to gain better data from the earlier results.{{sfn|Apollo 17 Preliminary Science Report|pp=20-1–20-2}} In addition, the S-band transponders in the CSM and LM were pointed at the Moon to gain data on its gravitational field. Results from the [[Lunar Orbiter]] probes had revealed that lunar gravity varies slightly due to the presence of [[Mass concentration (astronomy)|mass concentrations]], or "mascons". Data from the missions, and from the lunar subsatellites [[Apollo 15#Particles and Fields Subsatellite|left by Apollo 15]] and [[Apollo 16#Particles and Fields Subsatellite|16]], were used to map such variations in lunar gravity.{{sfn|Apollo 17 Preliminary Science Report|pp=14-1—14-2}}<ref name ="band:">{{cite web|publisher=[[Lunar and Planetary Institute]]|work=Apollo 17 Mission|title=Science Experiments – S-Band Transponder|date=2019|access-date=February 12, 2022|url=https://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/experiments/s_band/|archive-date=August 5, 2020|archive-url=https://web.archive.org/web/20200805010805/https://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/experiments/s_band/|url-status=live}}</ref>