Nimbus-B2 Press Kit

8/8/2019 Nimbus-B2 Press Kit

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NATIONAL AERONAUTICS AND SPACE ADMINISTRATION TEAS WO 2-4155NE W S WASHINGTON,D.C. 20546 WO 3-6925FOR RELEASE: WEDNESDAYA.M.

April 2, 1969

RELEASE NO: 69-50

p PROJECT: NIMus B2

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i . t GENERAL RELEASE-------- ---- --- ----------- ------------ ---- l-10NDMKBUS-B2 FACT SHEET------------------------------------ _-l-11-4NIMBUS AND SPACE APP LICA TIO NS------------------------------15-16C NIMBUS-B2 METEOROLOGICALEXPERIMENTS-----------------------1 -27NIMBUS RESULTS------------------------.------------------28-31LAUNCH VE.HICLFE--------------------------------------------32-38NIMBUS-B2 PROJECT OFFICIALS--------------------------------39-43

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NATIONAL AERONAUTICS AND SPACE ADMINISTRATION aLSo % 2415

NEWS WASHINGTON, D.C. 20546 wS 3-6925FO R RELEASE: IMMEDIATE

April 3, 1969

SPECITAL

NOTE TO EDITORS

The National Aeronaut ics and Space Administration jlaunch of th e Nimbus-B2 meteorological satellite has been

rescheduled for- one day ear l ie r than th e April 11 date

listed in the press kit (NASA Release No. 69-50). The

new launch day is April 10 at Western Test Range, Calif.

The launch window is 2:53 a.m. to 3:57 a.m. EST.

-end- 4/3/69

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NATIONAL AERONAUTIS AND SPACE ADMINISTRATION TELS WO 2-4155

NEWS WASHINGTON, D.C. 20546 WO 3-6925FOR RELEASE: WEDNESDAY A.M.

April 2, 1969

RELEASE NO: 69-50

NIMBUS-B2 SCHEDULED FOR LAUNCH

Another advanced Nimbus research an d development

weather observatory, carrying experiments that scientists

hope will ultimately lead to reliable long-range weather

forecasting, is scheduled to be launched April 11.

xTh e butterfly-shaped "weather-eye," weighing a

k record fo r meteorological satellites, 1,269 pounds, will

be launched by the National Aeronautics and Space Administra-

tion from the Western Test Range, Lompoc, Calif., with a

Thorad Agena-D rocket combination.

In addition to its primary role of meteorology, the

10-foot-tall observatory will obtain oceanographic data.

From orbit, it will communicate with sensors carried

aboard platforms such as floating buoys, balloons and air-

craft.

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NIMBUS B2 METEOROLOGICAL EXPERIMENTS

The Nimbus B2 wil l carry seven weather-measuring instru-ments, including Infrared Interferometer Spectrometer (IRIS),Satellite Infrared Spectrometer (SIRS), Interrogation Record-ing and Locations System (IRLS), High Resolution InfraredRadiometer (HRIR), Medium Resolution Infrarrd Radiometer (MRIR),Monitor of Ultraviolet Solar Energy (MUSE) &ld a daytime camera,Image Disector Camera (IDC).

The daytime camera and infrared radiometers are line scansystems. Each will generate one complete global nicture daily.

The other four instruments are being satellite-tested forthe first time.

Infrared Interferometer SpectrometerExperimenter: Dr. Rudolph H. Hanel, Goddard

This experiment will measure globally, the temperaturefrom top to bottom in the atmosphere, together with water vaporcontent and ozone distribution. The 35-pound sensor will alsoprovide data on gases in the atmosphere such as carbon dioxide,Nitrous oxide (N 2 0)* and methane (CH4).

Operating in the infrared spectral region, from 6 to 20microns (thousandths of a meter), IRIS will measure emittedradiation for determining temperature and ozone up to 15-milealtitudes, and water vapor up to 6 miles.

An important IRIS measurement wi l l be the ozone d i s t r i -bution because ozone, normally found in the upper part of the

Earth's atmosphere coverings absorbs incoming solar and out-going infrared radiation. It thus has an effect on the Earth'sheat balance an d on meteorological phenomena.

SThis instrument, with 'a 100-mile-diameter f ield of view,is a Michelson interferometer. IRIS analyzes the infraredspectrum radiated from the Earth's surface, or cloud tops,along the orbital path. During each 11-second viewinginterval, image motion compensation corrects for spacecrafttravel.

A computer compares the computed spectra with ideal blackbody curves conforming to Planck's radiation formula. Thus,

the basic source temperature and the local departures at 'various wave lengths are established. Thereby, the atmosphericcomposition, cloud height and other parameters may be determined.

The IRIS was built for NASA by Texas Instruments, Inc.,Dallas.

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NIMBUS B2 EXPERIMENT

Exper imenter an d Experiment Locat ion Purpose

NASA -- two f ixed pla t forms at Goddard Determine th e accuracy o f th e p o s i t i o nSpace F l i g h t Center determining techniques .

NASA -- mobi le va n Tracking exper iment to determine ifth e van ' s pos i t i on ca n be determineda s it r e tu rns to t h e E a s t C o a s t of t heU.S. from the Western Test Range inCa l i fo rn i a .

USAF A ir Weather Service -- weather Demonst ra te th e capab i l i t y l i nk ingreconnaissance aircraft AWS aircraft with weather and com-municat ions satellites fo r fu tu reroutine collection an d r ap id d i s -semination of operational weatherdata to appropriate world weathercenters.

National Center for Atmospheric Research Balloons will be released in Sioux(NCAR) -- two balloons Falls, S.D., to demonstrate and

evaluate the IRLS positioning capa-bility and also the capability ofrelaying meteorologic al data from abal loon to th e ground via satellite.

Off ice of Nav4al Research -- Floa t i ng ic e Evaluate IRLS pos i t i on ing accuracyisland (T 3 ) of a moving ice island, and demon-

strate thre capability of IRLS totransmit seismometer data from theplatform location in the Arctic toth e U.S. in 2-3 hours instead of theu s u a l weeks o r months.


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Experimenter and Experiment Location Purpose

Naval Oceanographic Office -- moored buoy off Determine wave height, surface currentPuerto Rico coast speed and sub-surface buoy depth.

Naval Oceanographic Office -- fixed platform Determine wave height, surface ter-on a Texas-type tower on Argus Island near perature, water velocity and sub-Bermuda surface temperature.

Woods Hole Oceanographic Institution -- one Measure water surface temperature, wateror two floating buoys in the Gulf Stream temperature at a depth of 985 feet andoff Cape Hatteras, and possibly one 490 feet, and the air temperatures abovefloating buoy on Georges Bank (off Cape the surface.Cod)

Bureau of Commercial Fisheries -- drifting Measure water surface temperature,buoy in the North Pacific Ocean south water temperature and pressure at aof Alaska depth of 165 feet, and salinity of

sea water at a depth of 3 feet.

Naval Air Systems Command -- two platforms Demonstrate rae us e of a satellite/in conjunction with air-sea rescue beacons IRLS system in the Air-Sea Rescue 0

Program.

National Science Foundation/Environmental Study weather/sea conditions in theScience Services Administration -- USNS Antarctica area.Eltanin (ship) operating in waters nearAntarct ic Continent


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High Resolution Infrared RadiometerExperimenter: Thomas Cherrix, Goddard

The 18-pound experiment, a scanning radiometer, willtake pictures of clouds and the Earth in total darkness.

Al l surfaces on Earth (even ice) emit infrared radiation

according to their temperature; ho t surfaces radiate moreintensely than cold.

Nimbus B2's HRIR senses radiation with a lead selenide

photo-electric cell which operates at minus 135 degrees F.

A strip about 1,500 miles wide, extending halfway arourd

th e globe (12,500 miles) on the night side of each orb i t is

scanned by a continuously rotating mirror which focuses th e

radiat ion on th e photo cel l .

The mirror sweeps across th is s t r ip some 75 times every100 seconds, thus covering the entire length of the strip with

about 2,300 continuous scans.

Nimbus' photo-electric cell converts theradiation stimulus

into electrical signals stored on magnetic tape aboard th espacecraft.

Pictures taker on the dark side of the Earthwill be read

ou t at Goddard while "live" pictures will be displayed onequipment at Automatic Picture Transmission stations anywhere

in the world as Nimbus B2 passes overhead.

A modification has been made to th e HRIR so the sensorcan also provide usefu l daytime pictures .

On each infrared picture, warm bodies of water such asthe world's seas and oceans appear very dark; land which iscooler at night than the oceans, appears somewhat lighter;and clouds which are generally much colder than water or land

surfaces vary from l i gh t grey to br i l l i an t white.

Since colder temperatures are usually found a t higheral t i tudes , clouds appear whiter with increasing al t i tude .

By studying infrared pictures, meteorologists can estimate

cloud height altitudes with an accuracy of ,o000 feet. Landand water surface temperatures can be determined with an

accuracy of about two degrees F.

HRIR has a resolut ion of flive miles a t picture center.It operates a t wavelengths of 3.4 to 4.2 microns in the infra-re d spectrum for night coverage and the visible region for

daytime coverage.

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The system was built by ITT Industrial Labs, Ft. Wayne,Ind.

Medium Resolution Infrared RadiometerExperimenter: Andrew W. McCulloch, Goddard

One of the main purposes of this experiment is to measure

the Earth's radiation balance, the difference between incomingan d outgoing radiation, to determine its long term effect onweather.

Another important meteorological objective is to ma patmospheric motion and jet streams. This can be accomplishedby comparing the radiation pictures obtained in the atmos-pheric window channel an d the two water vapor channels.

The patterns of water vapor distribution and of cirrusclouds resulting from such a comparison are closely related tothe dynamics of the atmosphere.

The 21-pound MRIR, a five channel radiometer, is designedto measure:

* Water vapor absorption -- this band, at 6.5 to 7.0microns, provides information on water vapor distribution.The energy observed in this channel is connected with therelative humidity of the upper atmosphere.

* Atmospheric window -- measures the temperature of theEarth in the 10-11 micron band where the atmosphere is trans-parent. These measurements provide information on the Earth'ssurface temperature in the absence of clouds or cloud toptemperatures. In addition, maps showing equal lines or radiant

emittance can be interpreted as cloud cover maps offering abackup to daytime and infrared pictures.

* Stratospheric temperatures -- this band, at 14-16 microns,provides a measurement of the temperatures in the lowerstratosphere by measuring the emission from the carbon dioxideabsorption band.

* Water vapor absorption -- this 20-23 micron band pro-vides information on atmospheric structure and water vapordistribution. The energy observed in this channel providesinformation on the relat ive humidity of the lower and middlesections of the atmosphere.

* Albedo radiation -- provides measurements of solarenergy levels in the visible and near infrared bands at 0.2 to4.0 microns.

The MRIR was built by the Santa Barbara Research Center,Santa Barbara, Calif., a subsidiary of Hughes Aircraft Co.

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Monitor of Ultraviolet Solar Energy (MUSE)Experimenter: Dr. Donald F. Heath, Goddard

Weighing nine pounds, this experiment will measure solarflux in five relatively broad spectral bands to detect varia-tion of relative intensity with time.

The ultraviolet energy input and its variation with timeat different wave lengths into the terrestrial atmosphere canbe related to the formation of the ionosphere, the establish-ment of photo--chemical equilibrium or ozone layer, and theheating of the upper regions of the stratosphere. This experi-ment will have the Sun in its field of view during most of thedaytime portion of the orbit.

The experiment was built by the Adcole Corp., Waltham,Mass.

Image Dissector Camera (IDC)

Experimenter: Gi l Branchflower, Goddard

This experiment is a line scan television system, with aresolution of about two miles at picture center. It will pro-vide a complete picture of the entire Earth daily.

This camera, weighing 14 pounds, will relay "live" pic-tures to small Automatic Picture Transmission stations andwill record pictures of the entire world for playback toGoddard.

Previous Nimbus an d ESSA weather satellites required twocameras to do the job of one IDC.

More than 400 APT stations will receive daytime photo-graphs about three times daily. Approximately 80 stationswill be operated in 43 nations or territories.

The IDC is completely electronic except for a protectivelens shutter which closes over the face of the sensor when thecamera is no t operating.

The experiment was built by IT T Industrial Laboratories,Ft. Wayne, Ind.

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SNAP-19 Radioisotope Thermonuclear GeneratorExperiment provided by Division of Space Nuclear Systems,Atomic Energy Commission

SNAP-l9 is one of a series of radioisotope thermoelectricgenerators (RTG), or atomic batteries, developed by the AtomicEnergy Commission under its SNAP (Systems for Nuclear Auxiliary

Power) program. The SNAP program is directed atdevelopment of

generators and reactors for use in space, on land arnd in the sea.Nimbus B2 will mark the first use of a nuclear power system ona NASA spacecraft, although syktems of this type have been used onNavy navigational satellites. (The SNAP-19 system is the sameone installed on the Nimbus B satellite.)

While the SNAP-19 is not the r, ar y power system for NimbusB2, this test flight is considered f logical and necessary stepan d a major milestone in the develL 'ment and acceptance of long-lived, highly reliable isotope pc. systems fo r space us e by NASA.

The characteristics of nuclear subsystems for a future

operationalsatellite will be assessed and up to 50 watts of

additional power will be available to supplement Nimbus B21ssolar cell. power system. It is expected that the output of thesolar power system will be decreased by space radiation andother factors in three months to a level below that required forspacecraft housekeeping and simultaneous operation of al l on-boardmeteorological experiments. The additional power provided by theSNAP-19 will permit full spacecraft operation for more than ayear. In addition, the SNAP-19 power ma y be of special importanceby providing power continuously in the event of a malfunction ofthe solar power system.

Description

The basic SNAP-19 unit is a 25-watt generator fueled withthe radio-isotope plutonium-238. The chemically inert fuel iscontained in a rugged 6-X 3-inch cylindrical capsule in thecenter of the generator. Each fueled generator weighs about 28pounds, is 11 inches high and 22 inches in diameter includingheat-radiating fins.

Two SNAP-19 generators will be mounted in tandem on theNimbus B2 satellite. They will provide about 50 ne t watts ofelectrical power. This power is in addition to the approximate211 watts to be provided by the satellite's large solar cellpaddles.

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Operation

In the generator, the spontaneous radioactive decay of theplutonium-238 generates heat. Thermoelectric elements convertthis heat directly into electrical energy. There are nomoving parts.

Advantages and Applications

Nuclear power is considered essential to the developmentof a long-lived, highly reliable, rugged, relatively small andlightweight electrical system for a variety of space applicationsincluding Earth orbital satellites, lunar missions and probes todistant planets. Present long-life spacecraft power systemsdepend on the us e of solar cells for generating power for directuse and for recharging chemical batteries. Ever-increa3ingpower requirements, however, are creating difficult problems inthe design of increasingly larger solar cell panels and associatedbattery storage systems. Additionally, nuclear power sources

would be required fo r any exploratory missions travelling greatdistances outward from the Sun. The size of solar cel l s requiredfo r such missions would be too large to be pract ical .

A SNAP generator has the potential of supplying many watts ofelectricity for several years. Since the operation of a SNAPgenerator does not depend on exposure to the Sun, only a minimalstorage battery system is needed for spacecraft operation. Theisotope power source is a rugged device in comparison to solarcells and is significantly less susceptible to radiation an d heatdamage.

Heat Source and Safety Considerations

The unique properties of plutonium-23 8 make it an excellentisotope for use in space nuclear generators. At th e end ofalmost 90 years plutonium-23 8 is still supplying half of itsoriginal heat. Since, in the decay process, plutonium-23 8

emits mainly the nuclei of helium, a very mild type of radiation,the generator which houses the fuel requires no shielding andthus avoids a weight penalty for radiation protection of thespacecraft hardware.

The Nimbus B2 satellite will be placed in a 600-mile-highpolar orbit and will remain in orbit for about l,600 years, bywhich time essentially al l of the plutonium-238 will have been

consumed through the radioactive decay process.The fuel form in the SNAP system is biological ly iner t and re -

presents no health hazard tc people or marine l i fe , and in mostabort cases it will be contained within its capsules.

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Before the use of the SNAP-19 system wa s authorized, athorough review was conducted to assure that no undue healthhazards existed to anyone involved in the launch or to thegeneral public.

For this review, extensive tests were conducted whichdemonstrated that the fuel would be safely contained under a llaccident conditions. 0

In the abort of the Nimbus B last May, the fuel capsulesremained in sea water at a depth of 300 feet for about fivemonths and, as expected, there wa s no release of fuel ordegradation of the capsules.

Development of SNAP Radioisotope Program

The first signif icant step in th e SNAP isotopic powerprogram was SNAP-3. This proof-of-principle device was intro-duced to the world by President Eisenhower in 1959.

Th e first isotopic space generator was put into serviceon June 29, 1961. The grapefruit-sized, five-pound, 2.7 wattgenerator, designated SNAP-3A*, was launched on a Navy naviga-tional satellite to supplement the satellitets solar power.The SNAP-3A generator marked i t s sixth anniversary l a s t June.At that time it had operated one year beyond i t s five-yeardesign l i fe . The satellite is still signaling intermittentlyto tracking stat ions around the world.

The AEC subsequently developed an advanced type of radio-isotope thermoelectric generator -- designated SNAP-9A -- whichweighs about 25 pounds an d generates 20 watts of power. SNAP-9Agenerators provided all of the power for two Navy navigationalsatellites launched in 1963.

Th e SNAP radioisotope program has brought forth new tech-nology which has resulted in the use of radioisotopes assources of compact, reliable, long-lived power on land, on seaand in space. SNAP generators have operated, are no w operating,or will operate in offshore o il platforms, weather stat ions,acoustic beacons, l ighthouses, navigational and weather sa te l l i t e s ,lunar experiments, deep sea and ocean bottom projects and otherpotent ial manned and unmanned space projects .

*SNAP radioisotopic devices are designated by oddnumbers, reactors by even.

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Contractors for SNAP-19

Isotopes Inc., Nuclear Systems Division Baltimore,designed, developed an d fabricated the SNAP-i9 generatorsfor the Nimbus B2.

Mound Laboratory, Miamisburg, Ohio, operated by MonsantoResearch Corp., fo r the AEC, fabricated the raw fuel into thefinal fuel form an d encapsulated the fuel.

Sandia Corp., a subsidiary of Western Electric, operatorof AECIs Sandia Laboratory, Albuquerque, New Mexico, providedtechnical direction fo r the SNAP-19 program.

Savannah River Laboratory, Aiken, S.C., operated by theDu Pont Co., for the AEC, prepared the ra w plutonium fuel.

Nimbus B Technological ExperimentExperimenter: R. Shelley, Goddard

Rate Measuring Package (RMP), is an alternate sourceof rate information fo r th e reaction wheel and gas je ttorquing devices in th e at t i tude and control system. It isa technological experiment o f one single-degree-of-freedom,rate-integrat ing gas-bearing gyro operating in a rate mode.The input axis of the gyro is oriented in the roll-yaw plane,45 degrees from the negative roll and the positive ya w axes.

I ts primary function is to provide data on th echaracteris t ics of gas-bearing gyros in the space environment..

The RMP was bu i l t for NASA by Sperry Gyroscope Co., GreatNeck, N.Y.

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NIMBUS RESULTS

Both Nimbus I and II, launched in 1964 and 1966,respectively, met or exceeded their objectives. Nimbus B.launched in May of 1968, never achieved orbit because therocket veered off course and had to be destroyed by the Range

Safety Officer.

Two Nimbus experimental satellites took about 1-millioncloud-cover pictures of the Earth. The day and night (infrared)pictures produced from these two observatories have givenmeteorologists a look at the Earth's cloud cover never beforepossible.

Meteorology

Meteorologists single out the APT camera (which providesinstant weather pictures to small ground stations anywhere)as the "single most significant contribution to meteorology

in the past twenty years."More than 400 APT stations are now scattered around the

world. In many parts of the world APT pictures are the major,and in some cases the only weather information source.

A number of private users in the United States andnumerous foreign countries have built their own receiversand facsimile machines at costs ranging from several hundredto several thousand dollars.

Many of the world's large airports have APT picturesfor commercial pilots to study before a flight. Pilots can

see what the weatner is currently like, during the day or atnight, from New York to London, or San Francisco to Tokyobefore taking off.

Nimbus II demonstrated for the first time, that infraredpictures could be read out 'live" on simple APT ground equip-ment.

Probably the most significant results from Nimbussatellites have been their ability to identify and track knownmeteorological phenomena such as hurricanes and typhoons, extra-tropical cyclones and frontal systems on a daily global basis,particularly during night time (infrared).

Storm system photographs have stimulated new studiesand new approaches to determining the morphology and lifehistory of storms.

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The radiation measurements obtained with Nimbus II'sMedium Resolution Infrared Radiometer (MRIR) experimentrender the best satellite observations ye t of the verticalstructure of the lower atmosphere.

Radiation measurements in the water vapor channel (6.4 -6.9 microns) permit inferences of the total water vapor con-tent in the upper atmosphere an d atmospheric dynamics.

These moisture patterns provide th e best means yet tomap, from a satellite, large scale stratospheric circulationan d the course of jet streams.

From HRIR and MRIR data, meteorologists have been ableto observe the course and intensity of the Intertropical Con-vergence Zone (ITCZ) as manifested by cloud formations girdlingth e globe near the Equator.

A typical set of infrared pictures was taken June 5, 1966,between 30 degrees North latitude and 30 degrees South latitude.Although activity wa s relatively weak on this day, th e courseof th e ITCZ was followed around the entire globe.

Pictures showed that the ITCZ generally follows th e 10degree North latitude parallel except over the Indian Oceanand Africa, where it dips down to the Equator. It is mostintense over India and Indonesia and all bu t disappears overportions of th e Pacific. Some lesser intensifications occurover Africa and South America. Over th e Central Pacific, aninteresting splitting into tw o narrow bands occurs.

Oceanography

It has been possible at night under certain cloud-freeconditions to detect areas of sharp temperature contrast, suchas currents and upwelling, from Nimbus HRIR photographs.

A study on large scale fluctuations of the Gulf Streamwa s based on Nimbus infrared pictures. Under cloudless skiesthe northern boundary of the Gulf Stream between Cape Hatterasand 60 degrees West wa s identified by the contrasting graytones on pictures over several months.

Nimbus infrared data were compared with informationcollected by a ship. Although a degree of uncertainty inboundary location arises from distortion in th e satellitephotos, comparisons suggest that continuity can be established.

The Gulf Stream boundary wa s seen on Nimbus photos inabout 50 cases. Other ocean current boundaries and pronouncedsea-surface temperature patterns, such as the Falkland and Bra-zi l Current discontinuity, the Agulhas Current and the KurohsiOCurrent could be seen from Nimbus infrared photographs.

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In one single infrared photo, oceanographers were able

to trace the meandering path of the Gulf Stream fo r 1,000miles.

Ice Pack Reconnaissance

High resolution television cameras and infrared radiometers

on Nimbus were able to "photograph" an iceberg in the WeddellSea. This is the first known case in which an iceberg has been'photographed from a satellite over the Arctic or Antarctic.

The iceberg wa s an estimated 71 miles long an d 20 mileswide.

Another series of Nimbus II pictures showed a southwarddrift of an individual iceberg along the Greenland coast over

a six-week period. Progress was observed regularly as it

followed th e major East Greenland Current.

By such satellite photography, circulation and sea ice drift

measurements ar e possible, adding ne w knowledge in the studyof the central Arctic environment.

Nimbus II, regularly covering the Antarctic areas,

presented possibilities fo r mapping extremely remote areas

where conventional techniques are at best difficult and ex-pensive.

Nimbus pictures of the Weddell Se a regions depict asemi-permanent coastline that is generally marked as a fixed

feature on charts of the Antarctic Ocean. Portions of this

coast have not been mapped fo r more than 20 years.

Numerous fractures in the pack ice appear in al l photo-graphs of this area, revealing enormous stresses and strainsin the ice.

Cartography aad Geology

Information obtained by Nimbus weather satellites

ha s also provided useful data fo r geographers and geologists

The U.S. Geological Survey, after studying more than

300 Nimbus I pictures over the Antarctic, found that relief

maps of the Antarctic were in slight error.

As a result, Mount Siple, a 10,000-foot high Antarcticmountain was repositioned 45 miles to the West. Nimbus I pic-tures of th e Kohler Range area at the Antarctic showed one

group of mountains, no t two as depicted on earlier maps.

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Geologists have used Nimbus photos to increase theirknowledge of past geologic formations in certain areas of theworld such as a river basin in Oregon, Paris Basin in CentralFrance and the Appalachian Mountains of Pennsylvania.

Snow Cover an d Hydrology

Snow depth of one inch or more can be detected byNimbus satellites as a continuous snow cover. Snow depthsof less than one inch have usually been detected, bu t oftendid not appear as continuous cover.

Areas with snow cover greater than about three inchesin nearly al l cases ha d reflectivities significantly higherthan areas with lesser snow depths.

Nimbus II APT pictures of the East Coast of the UnitedStates showed a very bright Delaware-Maryland-Virginia pen-insula blanketed the day before by an eight-inch snowfall.The rest of Maryland and Virginia had received only a traceto 4 inches of snowfall and thus showed lesser reflectivities.

Although present satellite photography cannot providethe quantitative (three dimensional) measurements of snowdepth provided by a network of surface stations, it can pro-vide th e limits of snow cover and detailed qualitative esti-mates of snow depth in the areas between reporting stations.

This information is of much importance to hydrologistsin making ground water run-off estimates and flood controlforecasts.

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i LAUNCHVEHICLE

The launch vehicle used for the Nimbus B-2 satellite isa Thorad-Agena-D rocket. The Thorad, or long tank Thor, isan uprated version of the Thrust Augmented Thor (TAT) used

in combination with an Agena secondstage to launch the first

two Nimbus weather satellites.

The Thorad booster has a 50 per cent greater tank volumethan previous Thors which increases engine burn time. PreviousThors carried 33,000 lbs. of RJ-l fuel and 67,000 lbs. of liquidoxygen. Thorad carried 45,000 lbs. of fuel and 100,000 lbs. ofoxidizer. Although no increase in thrust is realized, the mainengine burn time is increased from approximately 146 seconds toabout 218 seconds.

The three strap-on solid rocket motors used on theThorad are also uprated from the ones used on the TAT's. TheThorad strap-ons provide 52,130 lbs . of thrust for 37 seconds.This compares with 54,300 lbs . for 27 seconds for the old motors.

The greater propellant capacity of the Thorad coupled withthe new strap-on solid motors make it possible to boost about50 per cent more payload into Earth orbit than the originalTAT.

The Agena-D second stage is the same configuration usedin the past. Its 16,000-pound-thrust engine burns UDMH(Unsymetrical dimethylhydrazine) and IRFNA (Inhibited redfuming nitric acid). For the Nimbus mission 3,824 lbs . ofUDMHfuel is carried and 9,703 lbs. of IRFNA oxidizer.

The launch vehicle including the 18.7 foot Nimbus shroudstands 109.5 feet high. Because the spacecraft is designedto take cloud cover pictures near local noon during its south

, to north pass over the Earth, the possible launch time fromcomplex 2 of the Western Test Range is restricted. The launchwindow for April 11 is 2:53 p.m. to 3:57 p.m. EST.

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Sun-Synchronous Orbit

A high noon orbit is ideal for weather satellites becauseit provides maximum illumination for photographic purposes,and pictures of the Earth will always be taken at the same local

Su n Times every day. Night photos will be taken about midnightlocal time.

In a Sun-synchronous orbit, the preceission (eastward drift)of Nimbus will be about one degree daily, at the same rate anddirection as the Earth moves around the Sun. The Sun willalways be behind Nimbus during daylight orbit, which results inideal lighting conditions for cloud cover photography.

Countdown Milestones fo r Thorad-Agena-D Nimbus- Launch

Event Minutes

Countdown in i t ia t ion T-750

Thorad preparation T-750

WECO and Thorad telemetry checks T-730

Destruct checks T-680

Solid motor arming T-620

Gantry removal T-500

Agena tanking T-190

Agena pressurization T-95

Countdown evaluation and startterminal count T-60

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Typical Sequence Of Flight Events

Event Seconds

Liftoff 0

Start roll program 2

Stop roll program - start pitch program 16

Solid motor burnout 39

EJect solid motors 102

WECO steering commands commence 25

F Thorad Main Engine Cutoff 222

Thorad Vernier Engine Cutoff 231

Thorad-Agena--separati.on. 237

Agena first ignition 256

Agena first burn cutoff 487

Agena second burn ignition 3261

Agena second burn cutoff 3267

Nimbus separation 3517

* Begin Agena yaw and roll maneuver 3519

Fire first Agena retro 3710

Fire second Agena retro 6217

SECOR separation 6385

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Event /Tim~e (sec.) Statute Miles Statute Miles Vel/'MPH

Solid Motor Burnout /3 9 3.11 .683 1068

Solid Motor EJection 102 16.1 10.1 1520

MECO 22 2 59.8 141 8840

Thorad-Agena Separ tion 237 68.1178 8760

Agena first igni ion 256 77.3 225 8700

First Burn Cut If 487 97.5 995 18,100

Second Burn tion 3261 686 12,904 15,790

Second Burn Cutoff 3267 686 12,926 16,300

Nimbus Separation 3517 684.5 16,320

SECOR Se-paration 6385 682 ------ 16,320

/

/

J/

/a/


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Fl igh t Sequence

Thorad Phase

After liftoff, the Thorad-Agena vehicle rises verticallyfor about 16 seconds before beginning its pitch program.Starting at approximately two seconds after liftoff and continu-

ing until 16 seconds, the vehicle rolls to the desired flightazimuth of 193.77 degrees. Roll and pitchover are controlledby the Thorad autopilot programmer. The three solid rocketmotors provide thrust for approximately 39 seconds and areejected at about 102 after liftoff. Beginning at approximately125 seconds, the WECO ground guidance system corrects thelaunch vehicle trajectory by comparing the vehicle trajectorywith a predetermined t rajectory and then making small pi tchand yaw steering corrections.

Main engine cutoff o f th e Thorad is commanded by th eWECO guidance system along with the start of the Agena startsequence. A Thorad fuel depletion switch can also command

main engine cutoff.A ena Phase

Separation of the Agena stage is initiated by commandfrom the WECO ground station. Small retrorockets are ignitedto retard the flight of the Thorad first stage. Approximately12 seconds after separation the Agena and its spacecraft executea pitch maneuver followed by Agena engine start. Initialsteering correct ions are provided by the WECO ground s ta t ionwhich stops transmitting commands approximately 139 secondsafter engine start. First burn cutoff is determined by velocityof the Agena stage and is initiated by the Agena velocity meter.

The nose fairing which protects the Nimbus spacecraft Our-ing flight through the atmosphere is jettisoned approximately10 seconds after first burn ignition of the Agena main engine.

When velocity of the Agena reaches approximately 26,500feet-per-second, the Agena main engine shuts down and thevehicle begins a coast period.

During the 46-minute coast period the Agena vehicle andNimbus spacecraft continue or . a trajectory which takes italmost 12,000 miles measured along th e earth surface and froman alt i tude of 97 miles to an altitude of 686 miles. At thatpoint the Agena main engine is fired for about 6 seconds tocircularize the orbit.

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Hlirmbus Separation

Dufing the approximately 250 seconds between Agenaengine cutoff and spacecraft separation the vehiclepitches up so that it is a t an angle of ' about Z30 degreesin respect to the horizon. At T plus about 58 and ahalf mi.-Lutes explosive bolts are f i red on th e spacecraftadapter and compressed sprirns push the Nimbus spacecraftaway from the Agena stage at a rate of' about 415 I'eet-per-second.

Retromaneuver and Secor Separation

At two secornds after separation, a simultaneous roll,yaw maneuver is executed by the Agena. This maneuver resultsin the Agena flying roughly parallel to the Earth withits tail end forward. The first small retro engine is thenfired. This lowers the orbit of the Agena in relationshipto the Nimbus sF *eLlite.

At approximately 6,385 seconds into the flight anexplosive pin puller is fired freeing the SECOR from cheAgena and placing it in an orbit a fe w miles lower thainthat of the Nimbus.

A second retro maneuver places the Agena in an orbitwnere it will maintain a minimum separation of at least300 feet from the Nimbus spacecraft fo r a period o" atleast one year.


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L, nc h Ve n f c n e 'act Sneet

:horad-Agena-D an d Nimbus B2

: - e igh t on p a d : 10 9 ft. 5 *n.

.eight on p a d : 201 ,o37 lDs .

Thorad B o o s t e r Agena-D Upper Stage

Height : 70 ft. 6 in. 20 ft. d in.

Weigh t : i s 2 , 0 0 0 l b s . 17 ,517 lbs .

Propellants: 45,000 l b s . RJT-lJ fuel, 570 g a l l o n s unsymmet r i ca l100 ,000 lbs . Liqu id d i m e t h y l h y d r a z i n e (ULWH)oxsygen oxidizer

oxdz740 g a l l o n s inhibited

3 fuming nitric a c i d (IFRNA) 'I'l, I

T h r u s t : 317 ,050 l b s . total thrust 16 ,000 lbs . at altit-;ie

P r o p u l s i o n : Rocke tdyne M133 BLK 111, One regeneratively coc lc ra170 ,000 lbs . thrust eng ine ( B e l l AcrosystemF)

Three T h i o k o l TX-354-5 ,each 52 ,130 lbs. t h r u s t

Guidance : Pre -p rogrammed guidance up Agena Ih P (inertialto 120 sec . WECO on Agena r e f e r e n c e package) , n o r i z o nafter 120 sec . s e n s o r s , an d onboard f'lght

programmer.

Pr ime C o n t r a c t o r : McDcnne l l Douglas Corp. Lockheed M i s s i l e s an aSpace Co . , Sunnyva le ,Calif.


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NIMBUS B2 PROJECT OFFICIALS

NASA Headquarters, Washington

Leonard Jaffe Director, Space ApplicationsProgram

Dr. Morris Tepper Deputy Director, Space Appli-cations Program & Dir. ofMeteorology

Dr. Richard Haley Nimbus Program Manager

Bruton B. Schardt Deputy Nimbus Program Manager

Joseph B. Mahon Director, Launch Vehicle &Propulsion Programs

T.B. NorrisProgram Manager, Medium Launch

Vehicles

W.L. Lovejoy Agena Program Manager

Goddard Space Flight Center, Greenbelt, Md.

Dr. John F. Clark Director

Mr. Harry Press Nimbus Project Manager

Mr. Stanley Weiland Observatory Systems Manager

Dr. William NordbergNimbus Protect Scientist

Lewis Research Center, Cleveland

Dr. Seymour' C. Himmel Assistant Director for Rocketsan d Vehicles

H. Warren Plohr Agena Project Manager

Richard C. Geye Project Engineer

Kennedy Space Center, Fla.

Robert H.Gray Director, Unmanned Launch

Operations

H.R. Van Goey Manager, WTR Operations

W.S. Cortright Manager, Agena Operations, WT R

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U.S. Air Force

List to be provided by NASA Deputy for Space Systems,Headquarters b595th Aeoospaoe Test king

General Electric Co.

Mr . I.S. Haas Nimbus Project ManagerMissile and Space Division

McDonnell-Douglas Corp.

Mr. W. L. Duval Vice President, Director,Vandenberg Test CenterHuntington Beach, Calif.

Lockheed Missile & Space Co.

Mr. Ra y Gavlak Resident Manager - Space SystemsVandenberg AF Base, Cal'f.

U.S. Army Corps of Engineers

Joseph A. Bernard Acting Special Projects Officer,Directorate of Operations,U.S. Army Topographic Command,Corps of Engineers, EngineerTopographic Laboratories

Atomic Energy Commission

Milton Klein Director, Division of SpaceNuclear Systems

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Major Spacecraft Subsystem Contractors

Company Subsystem

ADCOLE Corp. Monitor ot ' Ultraviolet SolarWaltham, Mass. Energy

California Computer Products Command Clock, Medium Resolution

Lo s Ange]es,Calif. Infrared Radiometer ELectlroni(s

General Electric Co. Nimbus B2 integration an d test,Missile an d Space Division stabilization an d control sui,-Valley Forge, Pa. system, spacecraft structurec

an d antennas

Hughes Aircraft Co. PCM (Telemetry Transmitter)Culver City, Calif.

International Telephone & Tele- High Resolution Infrared Radio-graph, Industrial Laboratories meter an d th e Image DisectorFt. Wayne, Ind. Camera

T o c k h e e d Electronics Co. PCM TelemetryIndustrial Technology Division Tape RecorderEdison, N.J.

Radiation, Inc. PC M Telemetry an d th e InterrogatlonMelbourne, Fla. Recording an d Locations System

Radio Corporation of America High Data Rate Storage System,Astro Electronics Division Command Receivers, Solar PowerPrinceton, N.J. System an d th e Direct Readout

Infrared Transmit ter

Santa Barbara Research Center Medium Resolution Infrared Radio-Subsidiary of' Hughes Aircraft meterSanta Barbara, Calif.

Sperry Gyroscope Rate Measuring PackageGreat Neck, N.Y.

Texas Instruments Inc. Infrared Interferometer Spectro-

Dallas, Texas meter

Isotopes, Inc. SNAP-19Baltimore, Md.

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Launch Vehicle Contractors

CompanyResponsibility

BellAerosystems Company Agena

D Engine

Buffalo, N.Y.

Dcuglas Aircraft CompanyTHORAD (Long Tank Thor)

Missiles an d Space Systems Division

',anta Monica, Calif.

ElectrosolidsThor Autopilot

Los Angeles, Calif.

Minneapolis-HoneywellThor Autopilot

Minneapolis, Minn.

Texas InstrumentsThor Autopilot

Dallas, Texas

Lockheed Missiles an d Space Co.Agena D Vehicle (Airframe an d

Division of Lockheed Aircraft Co.Associated Electronics)

Sunnyvale, Calif.

RocketdyneTHORAD Engine

Division of Noruh American

Rockwell, Inc.Canoga Park, Calif.

Thiokol Chemical Corp. SolidPropellant Strap-on Boosters

Huntsville, Ala.

Western Electric Co.THORAD Guidance System

Burlington, North Carolina

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LAn'jor' GCrounld Equipment Contractor's

(.Qlnpany Hesponsitbi 1I ty

Ad I1 . p/We s t re x H1RIR Facsimile 1E-quipmentCommunications Divi~sion

ot' Lt1ton Systein.s-, Inc.New Rochelle, N.Y.

Atlied Research Associates, Inc. Operate the Nimbus DataConcord, Ma:;s. Utilization Centers

Caiif'orn Ia C"omputer P oducl-~s Ground : ta t ion Commnandi'on~Lco~ Angcele, Calif'.

Col I iz ; )radio Cco. 835-FP'oot Antenna Ground EetnuDallaz;, i'e'-xa.,

Control. Data Cor'pora'-ion Ground Staltion ~orniputevPsMirineapo 1.l s, Minn.

Electronic linage 3ystems Corp. Medium Resolutli)n IritraredBoston, Mlass. Radi ometer Film Pr'oces;I ng,

Equi~pmen t

General E'Lectric Co. Operate the Nimous COritVoLMiosi~le & Space Division C,.ent rValley Forge, Pa.

Lear, 31egler Inc. Computer~ ,-Jystem f'or ProcessinL;Anaheim, Calif ' . Medium Resolution Inf'raredl

Radiometer Data

Photo Mechanisms, Inc. Rapid Film Processing S3ystern f'orHuntington Station, N.Y. Image D15sector' Camera Photo.-

graphs

Radiation. Inc. Operate VCM Telemetr.v iEquipmentMelbourne, Fla.

RCA Service Co. Operate the Nimbus Data HandlingCherry Hill, N.J. System

Nimbus-B2 Press Kit

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