lageos press kit

8/7/2019 Lageos Press Kit

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National Aeronautics andSpace AdministrationWashington. D.C. 20546AC 202 755-8370

For Release IMMEDIATE

Press Kit Project LageosRELEASE NO: 76-67

ContentsGENERAL RELEASE ...................... ........... . 1-5MISSION OBJECTIVES. .............. ...... - 6PROGRAM BACKGROUND ............................ . 7COLLECTING DATA FROM LAGEOS.................... 7-8LAGEOS DESCRIPTION. * * * *.*.*.*.*.*.*.*.*............................ 9-12MESSAGE TO THE FUTURE .............................. . 12-14LAUNCH SEQUENCE ................................. . 15-17DELTA LAUNCH VEHICLE DESCRIPTION .............. 18-20LAUNCH OPERATIONS.............................. 20LAGEOS/DELTA PROGRAM/PROJECT MANAGEMENT ....... 21-23


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National Aeronautics andSpace AdministrationWashington, D.C. 20546AC 202 755-8370

For Release:Bill O'DonnellHeadquarters, Washington, D.C. IMMEDIATE(Phone: 202/755-8487)

Don WorrellMarshall Space Flight Center, Huntsville, Ala.(Phone: 205/453-0035)

RELEASE NO: 76-67

SATELLITE MAY AID IN UNDERSTANDING EARTHQUAKE MECHANISMS

A satellite which looks like a giant golf ball will belaunched by NASA next month into a 5,900-kilometer (3,600-mile) high orbit to serve as a tool for obtainino informationon Earth's crustal movements, polar motion, solid Earth tidesand precise locations of various spots on Earth.

The Laser Geodynamic Satellite (Lageos) is scheduled forlaunch aboard a Delta rocket from the Western Test Range inCalifornia May 4 at 4 a.m. EDT.

Lageos will use and demonstrate the capability of lasersatellite tracking techniques to make extremely accuratemeasurements of Earth's rotation and movement of the Earth'scrust.

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The useful life of Lageos is estimated at up to 50 yearsbut it will remain in orbit for more than 8 million years.

One important benefit of the pin point accuracy of suchmeasurements could be in a better understanding of the mech-anisms which cause earthquakes. NASA expects the U.S. Geo-logical Survey, which is responsible for earthquake researchand prediction, to use Lageos to make minute measurements ofmovements of large land masses called tectonic plates, aswell as specific measurements along critical faults, such asthe San Andreas fault in California.

Lageos is a solid, heavy, passive satellite with nomoving parts or electronic components. Its extremely stablecircular orbit will allow it to serve as a geodetic referencefor ground observations to be made in support of NASA'sEarth dynamics programs.

Lageos is an aluminum sphere with a brass core about60 centimeters (24 inches) in diameter and weighs 411 kilo-grams (903 pounds).

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It carries an array of 426 prisms called cube-cornerretroreflectors, giving it the "dimpled" appearance of a

i golf ball.

Retroreflectors are three-dimensional prisms thatreflect light -- and, in this case, a laser beam -- backto its source, regardless of the angle at which it is re-ceived. The Lageos retroreflectors are made of high-qualityfused silica, a synthetic quartz.

A laser pulse beamed from a ground tracking-receivingstation to Lageos initiates a timing signal at the groundstation that continues until the pulse is bounced back fromthe satellite and received at the station. By measuringthis length of time, the distance between the station andthe satellite can be calculated. This process is known aslaser ranging.

Movements of the Earth's surface as small as 2 cm(8 in.) can be determined using this technique. By tracKingLageos for a period of several years, characteristics ofthese motions can be determined, and perhaps correlated withobserved Earth dynamics phenomena.

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Lageos will be launched into a circular orbit of 5,900km (3,600 mi.) altitude with an inclination of 110 degreesto the equator. This is high enough to allow simultaneousobservations between stations on different continents.

Immediately after separation of the satellite from theapogee kick stage, some tracking data will be available onthe satellite's location by means of a small tracking beaconattached to the kick stage. This data will be used initiallyto target optical tracking instrumentation.

Smithsonian Astrophysical Observatory (SAO) cameras willuse the orbital predictions from the tracking beacon data to.acquire and photograph Lageos against star fields for a fur-ther refinement df orbital position. Using this SAO cameradata, the laser ground stations with their narrow beams willbe able to locate and reflect off the satellite.

The Lageos project is part of the Earth and OceanDynamics Application Program (EODAP) being conducted by theNASA Headquarters Office of Applications.

NASA's Marshall Space Flight Center, Huntsville, Ala.,has management responsibility for the design, developmentand launch of the satellite.

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NASA's Goddard Space Flight Center, Greenbelt, Md.,has responsibility for the launch vehicle,provision of thesolid fuel apogee kick motor and elements of the spacecraftinvolved in its mounting and separation from the launchvehicle and for the continued mission operations of theground stations that track and range the satellite.

NASA's Kennedy Space Center, Fla., is responsible forthe Lageos launch operations. The KSC Unmanned LaunchOperations Western Launch Operations Division is locatedat Vandenberg Air Force Base near Lompoc, Calif., where thelaunching will take place.

Program cost, including the satellite and launchvehicle is about $8.5 million.

(END OF GENERAL RELEASE. B?.CKGROUND INFORMATION FOLLOWS.)


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MISSION OBJECTIVES

Lageos is the first NASA satellite dedicated exclusivelyto laser ranging. It will provide the first opportunity toevaluate satellite laser ranging using a satellite that ismore stable than posicions on Earth.Lageos mission objectives are to provide a referencepoint for laser ranging experiments such as: the monitoringof the motion of tectonic plates, the description of the time-varying behavior of the Earth's polar positions, the main-tenance of geodetic reference systems and th e more accuratedetermination of universal time.The Lageos project represents the first step in thesolid-Earth dynamics portion of the NASA Earth and OceanDynamics Applications Program (EODAP).Through this program NASA intends to use space andspace-derived techniques for precise monitoring of the Earth'scrustal motions (tectonic plate movement, fault motions,polar wobble and rotational rate) to contribute to develop-ment of an understanding of earthquakes, their origin andthe ability to forecast their occurrence.NASA in the EODAP proQram also monitors ocean phenomenasuch as sea state, currents, surface winds and general oceancirculation on a global basis. Such observations are impor-tant to the maritime industries.Seasat Ocean Dynamics Satellite, scheduled for launchin 1978, will provide data on wave height, wind speed, windand wave direction, ocean temperature and ocean surfacetopography. Lageos and its laser ground stations will beused to determine the exact location of stations to be usedin calibrating the altimeters on Seasat.

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PROGRAM BACKGROUND

The idea of orbiting a compact spherical satellite forlaser ranging had been discussed at least as early as thefirst successful satellite laser observations in 1964. Hlow-ever, substantial improvements in satellite tracking accuraciesrequired some'means of attenuating the effects of atmosphericdrag and solar photon pressure. One way to do this would beto use a very dense spherical satellite. Even in 1964, theaccuracy of laser tracking instrumentation was high enough tomake this concept attractive.A strong motivation for attaining orbit accuracies of

10 cm (4 in.) or better emerged from a seminar on solid-Earthand ocean physics convened by NASA at Williamstown, Mass., inAugust 1969. Geophysicists at this seminar suggested thatsatellite techniques be applied to the measurement of crustalmotions, both on a global scale and in somewhat more detailin active fault zones. This new information would increaseunderstanding of solid-earth dynamics and earthquake research.

COLLECTING DATA FROM LAGEOS

Lageos investigations will be carried out in two phasesand will take many years to complete. The validation/appli-cations phase will take the four years during which measuringaccuracies to better than 10 cm (4 in.) will be perfected.Measurement techniques developed and validated during Phase Iwill be applied during the post-1980 years. As a result, andas more stations are added to the network, ultimately up to14, accuracies will improve to better than 5 cm (2 in.).

Lageos scientists expect to measure tectonic platemotion using a global network of tracking stations. The goalis to detert shifts in the massive plates underlying the Earth'ssurface to within one centimeter (.4 in.) per year averagedover four years. This could be important in understandingand possibly forecasting earthquakes, changes in polar motion,Earth and ocean tides, Earth rotation and vertical motionsbetween sites.

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There will be both stationary and mobile laser rangingstations. Two stations on each tectonic plate will be re-quired to provide data on plate motions. Three or more st-a-tions will monitor each fault. Nine stations, seven mobile,are planned by 1978.

The mobile stations will spend an average of fourmonths at a site. One or two months will be required fortransportation tc the next site. Sites will be reoccupiedon two-year cycles. Thirteen laser tracking locations forthe mobile stations are required and are designed so thatthe mobile system can be relocated to within one-tenth ofa centimeter (.04 in.) of the position previously occupied.

These measurements from the different locations willprovide the base from which plate motions can be determinedby analyzing variations in locations of the different siteswith respect to each other.

The project will be conducted in collaboration withother government agencies, the Smithsonian AstrophysicalObservatory network of four laser stations and with sitesand laser stations in foreign countries.

All data will be sent to Goddard Center for archivalpurposes and for dissemination to investigators. SAO alsowill disseminate data returned from its network and forwardit to Goddard for archival purposes.Fault Measurements

Observations of changes in plate movement acrossselected faults, such as the San Andreas Fault in California,will be given priority and are expected to be important inunderstanding the occurrence of earthquakes in this area ofthe Uni.ted States. Fault measurements to within a few centi-meters are planned for the next six to eight years.

Goddard Center has been conducting a laser measuringproject called the San Andreas Fault Experiment (SAFE) forthe past four years, in cooperation with universities andother government agencies. The project is designed to detectshifts occurring along the boundary of the North American andPacific plates to aid in developing a tectonic model of thewestern United States.

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LAGEOS DESCRIPTION

Mass 411 kg (903 lb.)Diameter 60 cm (24 in.)Number of retroreflectors 426

Diameter 3.8 cm (1.5 in.)Material:

Hemispheres AluminumCore BrassAttached fittingand nuts Stainless steelRetroreflectors Fused silicaRetroreflector mounts KEL-F (plastic)

The aluminum sphere, retroflector mounting hardwareand handling fixture for the satellite were designed, devel-oped and manufactured by Marshall Space Flight Center.The design of Lageos evolved from several trade-offs

which proved necessary for achievement of program objectives.For example, the satellite had to be as heavy as possible inorder to offset the effects of drag and of variations inEarth's gravity, yet light enough to be placed in a highorbit by the Delta launch vehicle.The satellite had to be big enough to accommodate alarge number of retroreflectors, but small enough not to beaffected by solar radiation drag. Aluminum would have beentoo light for the entire body of the sphere, while brass

would have weighed too much. Design engineers finally de-cided on combining two aluminum hemispheres bolted togetheraround a brass core to provide a large mass/surface ratio.Materials were selected to reduce magnetic effects betweenthe satellite and the Earth's magnetic field.

Initial plans were to build both a full-scale prototypeground test satellite and a flight satellite. When the plannedground test model completed basic testing without adverseeffects, a decision was made to use it as the flight unitand eliminate duplication.

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The Lageos orbit was selected to reduce gravitationaldistortions and the satellite itself has been optimized tomaintain a precise stable orbit that will last for millionsof years. Because there are no active parts, Lageos willgive geophysicists a stable reference system from which toaccurately measure relative crustal motions of the Earthfor many decades.

MESSAGE TO THE FUTURE

A message has been sealed inside Lageos in the eventit should be retrieved from crbit or discovered after itsreturn to Earth some 10 million years from now.The message was prepared by Dr. Carl Sagan of theLaboratory for Planetary Studies at Cornell University,Ithaca, N.Y. Two copies of the message, which is etched onstainless steel sheets measuring 10 by 18 cm (4 by 7 in.),are installed in the satellite -- one at each end of thebolt connecting the two hemispheres which make up Lageos.In its upper center the message displays the simplestcounting scheme, binary arithmetic, which uses only zerosand ones. The numbers one through 10 in binary notationare shown. At upper right is a schematic drawing of theEarth in orbit around the Sun, an arrow indicating thedirection of motion. The arrowhead points to the right,the convention adopted for indicating the future. Allarrows accompanying numbers are such "arrows of time."Under the Earth's orbit is the binary number one, denotingthe period of time used on the plaque -- one revolution ofthe Earth about the Sun, or one year.The remainder of the Lageos plaque consists of threemaps of the Earth's surface, all in a common projection whichpermits the entire surface of our planet to be viewed at once.Beneath the first map is an arrowhead pointing left, denoting

the past, and connected to a large binary number. In decimalnotation this number is equivalent to about 268 million yearsago. The map shows the approximate configuration of the con-tinents in the Permian period, about 225 million years ago.The binary number could have been made more accurate, butwas "rounded off" to avoid giving the impression of spuriousaccuracy. Since detailed knowledge of continental drift isstill very limited, all the continents are shown together inone mass, sometimes called "Panaaea."

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The close fit of South America into West Africa wasone of the first hints that continental drift actuallyoccurs. Australia is shown as lying originally betweenAntarctica and West Africa; in other reconstructions, itis thought to have been in contact with Western Antarctica.These maps are not intended to be a precise representationof continental drift, but rather a means of portrayingdramatically the existence and extent of continental drift.The middle map displays the present configuration ofthe continents. Below it is a symbol indicating zero years,and arrows denoting simultaneously the past and the future;that is, the present. This map represents the zero point

in time for the other two maps. Lageos is shown beinglaunched into space from the Western Test Range at VandenbergAir Force Base in California.The final map is coded by an arrow pointing to theright and a binary number, again rounded off, denoting anepoch 8.4 million years from now -- very roughly, the esti-mated lifetime of the Lageos spacecraft. The satellite isshown returning to the Earth. Many important changes inthe Earth's surface are shown, including the drift ofVandenberg Air Force Base and the rest of Southern Californiaout into the Pacific Ocean. This separation, along the SanAnareas Fault, is an expected consequence of the crustalmotions which Lageos is designed to investigate. Many ofthe other changes in the map of the Earth shown are littlemore than guesses. Our knowledge of them should be signifi-cantly improved by Lageos.Whoever comes upon the Lageos plaque need only comparea current map of the Earth's geography with that in thelower two maps to calculate roughly the time between hisown epoch and ours. Drift rates of about an inch per yearcan, in fact, be estimated by comparing the bottom two maps.Thus, the prime objective of Lageos and the method of tellingtime of the spacecraft's plaque are identical.Lageos will return to Earth at a time in the futuremore distant than the timne in the past of the origin of thehuman species. The Earth will surely have changed profoundlyby that future time and not only with respect to the d-spo--sition of its continents. Whoever is inhabiting Earth inthat distant epoch may appreciate a little greeting card fromthe remote past.

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