Milestone-Proposal:Apollo 11 Lunar Ranging Experiment (LURE)

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Docket #:2018-08

This Proposal has been approved, and is now a Milestone


To the proposer’s knowledge, is this achievement subject to litigation? No

Is the achievement you are proposing more than 25 years old? Yes

Is the achievement you are proposing within IEEE’s designated fields as defined by IEEE Bylaw I-104.11, namely: Engineering, Computer Sciences and Information Technology, Physical Sciences, Biological and Medical Sciences, Mathematics, Technical Communications, Education, Management, and Law and Policy. Yes

Did the achievement provide a meaningful benefit for humanity? Yes

Was it of at least regional importance? Yes

Has an IEEE Organizational Unit agreed to pay for the milestone plaque(s)? Yes

Has an IEEE Organizational Unit agreed to arrange the dedication ceremony? Yes

Has the IEEE Section in which the milestone is located agreed to take responsibility for the plaque after it is dedicated? Yes

Has the owner of the site agreed to have it designated as an IEEE Milestone? Yes


Year or range of years in which the achievement occurred:

1969

Title of the proposed milestone:

Apollo 11 Lunar Ranging Experiment (LURE), 1969

Plaque citation summarizing the achievement and its significance:

On 1 August 1969, the first accurate measurement of the distance between the earth and the moon was determined by firing a laser from Lick Observatory at retro-reflectors placed on the moon by Apollo 11 astronauts, then measuring the time delay for detection of the reflected beam. The gigawatt-powered ruby laser was manufactured by KORAD Lasers in Santa Monica, Calif.

200-250 word abstract describing the significance of the technical achievement being proposed, the person(s) involved, historical context, humanitarian and social impact, as well as any possible controversies the advocate might need to review.


IEEE technical societies and technical councils within whose fields of interest the Milestone proposal resides.


In what IEEE section(s) does it reside?

Site 1: Santa Clara Valley Section; Site 2: Southern California Council

IEEE Organizational Unit(s) which have agreed to sponsor the Milestone:

IEEE Organizational Unit(s) paying for milestone plaque(s):


IEEE Organizational Unit(s) arranging the dedication ceremony:


IEEE section(s) monitoring the plaque(s):


Milestone proposer(s):


Please note: your email address and contact information will be masked on the website for privacy reasons. Only IEEE History Center Staff will be able to view the email address.

Street address(es) and GPS coordinates in decimal form of the intended milestone plaque site(s):

Site 1: the Shane 120-inch Reflector Telescope Dome on Mt. Hamilton above San Jose, CA, at Lick Observatory (one of the Univ. of California Observatories); Site 2: at Water Garden, 2450 Colorado Ave., Santa Monica, CA, a major new office and shopping complex whose tenants include Amazon Studios and CBS Global Distribution Group.

Describe briefly the intended site(s) of the milestone plaque(s). The intended site(s) must have a direct connection with the achievement (e.g. where developed, invented, tested, demonstrated, installed, or operated, etc.). A museum where a device or example of the technology is displayed, or the university where the inventor studied, are not, in themselves, sufficient connection for a milestone plaque.

Please give the address(es) of the plaque site(s) (GPS coordinates if you have them). Also please give the details of the mounting, i.e. on the outside of the building, in the ground floor entrance hall, on a plinth on the grounds, etc. If visitors to the plaque site will need to go through security, or make an appointment, please give the contact information visitors will need. Site 1: the first accurate measurement of the distance between the earth and the moon took place in the Shane 120-inch Reflector Telescope Dome on 1 August 1969; Site 2: Water Garden is within one block of the building where KORAD Lasers invented, designed, manufactured and tested the ruby-crystal laser system used in the LURE.

Are the original buildings extant?

Site 1: Yes, the Shane 120-inch Reflector Telescope Dome still exists, and this telescope remains in active use by numerous astronomers; Site 2: No.

Details of the plaque mounting:

Site 1: on the wall of the lobby at the front entrance of the Shane 120-inch Reflector Telescope Dome building; Site 2: on an outdoor pedestal by Colorado Ave. at the Water Gardens complex.

How is the site protected/secured, and in what ways is it accessible to the public?

Site 1: the Shane 120-inch Reflector Telescope Dome building is open to the public during business hours on weekdays, and from 10am-5pm on weekends; Site 2: the pedestal onto which the plaque will be mounted will be secured into the ground, and the Water Gardens complex has 24-hour security guards.

Who is the present owner of the site(s)?

Site 1: the Univ. of California Observatories; Site 2: the City of Santa Monica, CA.

What is the historical significance of the work (its technological, scientific, or social importance)? If personal names are included in citation, include justification here. (see section 6 of Milestone Guidelines)

"The scientific and engineering achievement of LURE—which aimed at using lasers to precisely measure the distance between the Earth and the moon—held huge potential strategic value, both military and commercial." [Ref1: Optics & Photonics News] at p. 45.

"The Apollo 11 Laser Ranging Retro-Reflector (LRRR) was designed by a team of scientists and engineers to serve as a reference point on the lunar surface to be used in continued monitoring of the point-to-point distances between it and stations on earth by the technique of short-pulse laser ranging." [Ref2: Science Magazine 1970] at p. 368.

Hal Walker, Jr., "a former U.S. Navy electrician’s mate, was the key man on station at Lick Observatory in California manning his team’s 1.2-GW ruby-crystal laser. On [1 August 1969], he fired KORAD’s laser at the moon and received a successful ranging signal—thus beating the Soviets to the punch, and earning Walker a place in engineering history." [Ref1: Optics & Photonics News] at p. 42.

The weapons-grade ruby-crystal KORAD laser system used in the Apollo 11 Lunar Ranging Experiment (LURE) that was the first laser to successfully complete the experiment was invented, designed, manufactured, and tested at KORAD Lasers in Santa Monica, Calif. The laser was then transported to Lick Observatory in preparation for the Apollo 11 mission. After the Apollo 11 astronauts placed the Lunar Ranging Retro-Reflector (LRRR) array in the Sea of Tranquility on the surface of the moon, scientists and engineers began the process of locating the Array using broad sweep laser shots fired through the telescope at Lick Observatory.

By the time the laser beam reached the moon, it is estimated to have been spread across an area in excess of 2 km in diameter. Thus the ability to hit the targeted Array was essential to getting an appropriate recognizable signal from the return photons. Filters were used to remove ambient light and to capture the red photons at 6943 Angstroms, and photo-multipliers were used to count photo-electrons through a time-delayed gate that collected and measured the return signal strength.

During the setup and target acquisition phase of the LURE, some of the components of the KORAD laser had exploded due to the high voltage and high power discharges, potentially terminating the KORAD ranging. This kind of failure was in fact the fate of a competing laser system manufactured by SpaceRays that has also been operating at Lick Observatory. Hal Walker, Jr. of the KORAD team drove from Lick Observatory to Santa Monica (a trek of over 350 miles) to pick up replacement parts, and returned with them to Lick Observatory.

In parallel with the two team working at Lick, teams at the McDonald Observatory in Fort Davis, TX, and at the Haleakala Observatory in Kula, Maui, Hawaii, were also involved in the LURE. In addition, much to the surprise of everyone, the Cold War entered the picture when scientists in the USSR started firing lasers at the Sea of Tranquility in order to attempt to beat the US to a successful ranging measurement.

The KORAD team at Lick Observatory went on to complete 169 successful laser shots at the target which each measured the round trip time to the Moon. "Acquisition measurements of the round-trip travel time of light, from the McDonald Observatory to the Laser Ranging Retro-Reflector deployed on the moon by the Apollo 11 astronauts, were made on 20 August and on 3, 4, and 22 September 1969. The uncertainty in the round-trip travel time was +/- 15 nanoseconds, with the pulsed ruby laser and timing system used for the acquisition." [Ref2: Science Magazine 1970] at p. 368.

The Apollo 14 and Apollo 15 missions each included placement of an LRRR array on the Moon in 1971, and the USSR also placed two of its own LRRR arrays in 1970 and 1973. Laser ranging experiments continue to this day, making them the only continuing active science projects from that era.

The NASA Apollo 11 Preliminary Science Report of October 1969 is an important historical record with its detailed description of this experiment and its earliest results, numerous photographs taken by the Apollo 11 astronauts, a diagram showing placement of the retro-reflector array within Tranquility Base, and information about the other scientific experiments undertaken by the Apollo 11 crew. [Ref3: NASA Apollo 11 Report] at pp. 3-4, 51, 89 and 163-182.

What obstacles (technical, political, geographic) needed to be overcome?

Technical Obstacle #1: Sending a manned mission to the Moon and placing a retro-reflector on the lunar surface. This was first accomplished by the Apollo 11 astronauts positioning a retro-reflector on July 20, 1969. In late 1970, the Soviet Union's Luna 17 spacecraft carried the second retro-reflector to the Moon along with Lunokhod 1 (Луноход, moon walker in Russian), an unmanned lunar rover. Lunokhod 1 was the first remote-controlled robot "rover" to freely move across the surface of an astronomical object beyond the Earth, and the Soviet retro-reflector was used to determine its location.

Technical obstacles #2 (building and operating a gigawatt-powered laser system based on a weapons-grade ruby-crystal laser), #3 (finding a tiny target on the lunar surface) and #4 (detecting between 1 and about 10 reflected photons): "Two contractors were chosen to create the high-powered laser systems that would serve as the Earth-bound component of the LURE project: Spacerays Corporation and KORAD Laser Systems." "Each KORAD laser system had a unique set of challenges due to the developmental nature of the technology, so it was not a simple matter of firing at will to hit the retroreflector on the moon." "In the end, success depended less on chance than on technological readiness. Some teams encountered catastrophic equipment failures due to the high-powered nanosecond pulses, which literally broke down the molecular structure of the air around the equipment, complete with thunderous bangs and fried electronics. System-design thresholds and even sabotage were also claimed as sources of failure. In other cases, with beam-widths at the surface of the moon dispersed as wide as 7 km, there was just not enough transmitted energy to produce a recognizable signal from the few photons that returned to the Earth." "Success came at last to Walker and his team in the early morning hours of 1 August 1969. A few days earlier, Walker’s team’s laser had experienced its own catastrophic failure and had to be replaced with a unit from KORAD’s labs in Santa Monica, 350 miles south of Lick Observatory. Hal himself raced down Mount Hamilton in a rented car to get to KORAD, pick up the replacement parts, then return to Lick and get the equipment installed and operational for the next round of shots." [Ref1: Optics & Photonics News] at pp. 45 and 46.

Political Obstacle #1: Finding the retro-reflector on the lunar surface before the Soviets did: "Four U.S.-based teams equipped with high-powered lasers then began a painstaking search for the minuscule retroreflector target nearly a quarter-million miles away—the array’s exact coordinates in the Sea of Tranquility being unknown. The teams, each armed with a laser system, were stationed at McDonald Observatory in Texas, Mount Haleakala Observatory in Hawaii, and two laser teams at Lick Observatory in California." "It soon became apparent to the U.S. scientists scrutinizing the Sea of Tranquility, however, that someone else on Earth was also firing ruby-red beams at the moon and attempting to hit the LURE array. Those rogue laser shots, it turned out, were from a team of Soviet scientists, who hoped to achieve an end run around the U.S. groups. There was, of course, no way to stop the Soviet team from trying—but as [Hal] Walker reports, the American teams were told in no uncertain terms by their NASA and DARPA sponsors, 'Don’t let the Soviets hit our mirrors!' The race was on between the lunar laser-ranging teams." [Ref1: Optics & Photonics News] at p. 46.

What features set this work apart from similar achievements?

An accurate measurement of the distance to the Moon was not possible until a retro-reflector was placed on the lunar surface. The Apollo 11 astronauts first did this on 20 July 20 1969, and 1 August 1969 is the date of the first accurate measurement of the distance to the Moon.

The reflector experiments were to be used for more than simply determining an accurate Earth-Moon distance, including permitting "precise measurements of the lunar orbital motion, lunar librations, the lunar radius, fluctuations in the earth's rotation rate, Chandler wobble of the earth's axis, intercontinental drift rate, and a possible secular change of the gravitational constant." [Ref4: Science Magazine 1969] at p. 100.

Supporting texts and citations to establish the dates, location, and importance of the achievement: Minimum of five (5), but as many as needed to support the milestone, such as patents, contemporary newspaper articles, journal articles, or chapters in scholarly books. 'Scholarly' is defined as peer-reviewed, with references, and published. You must supply the texts or excerpts themselves, not just the references. At least one of the references must be from a scholarly book or journal article. All supporting materials must be in English, or accompanied by an English translation.

[Ref1: Optics & Photonics News] [Ref2: Science Magazine 1970] [Ref3: NASA Apollo 11 Report] [Ref4: Science Magazine 1969]

Supporting materials (supported formats: GIF, JPEG, PNG, PDF, DOC): All supporting materials must be in English, or if not in English, accompanied by an English translation. You must supply the texts or excerpts themselves, not just the references. For documents that are copyright-encumbered, or which you do not have rights to post, email the documents themselves to ieee-history@ieee.org. Please see the Milestone Program Guidelines for more information.


Please email a jpeg or PDF a letter in English, or with English translation, from the site owner(s) giving permission to place IEEE milestone plaque on the property, and a letter (or forwarded email) from the appropriate Section Chair supporting the Milestone application to ieee-history@ieee.org with the subject line "Attention: Milestone Administrator." Note that there are multiple texts of the letter depending on whether an IEEE organizational unit other than the section will be paying for the plaque(s).

Please recommend reviewers by emailing their names and email addresses to ieee-history@ieee.org. Please include the docket number and brief title of your proposal in the subject line of all emails.