orbiting solar observatory s-16 press kit

8/8/2019 Orbiting Solar Observatory S-16 Press Kit

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P9XA-/0o 35%NATIONAL AERONAUTICS AND SPACE ADMINISTRATION TELS. WO 2-4155NEWS V/ASHINGTOND.C. 20546 WO 3-6925

FOR RELEASE:FOR RELEASE A.M.'s ThursdayFebruary 22, 1962

RELEASE NO. 62-32

OSO FACT SKEETPROJECT: Orbiting Solar Observatory (S-16)PROJECT DIRECTIONAND MANAGEMENT: NASA Goddard Space Flight Center,Greenbelt, Md., Dr. John C. Lindsay,Project Manager and Project Scientisi;;George R. Smith, Project Coordinator.PRIME CONTRACTOR: Ball Brothers Research Corporation,

Boulder, Colorado, Dr. R. C. Mercure JLbDirector; Dr. David S. Stacey, TechnicalDirector.MAJOR OBJECTIVES: Measure solar electromagnetic radiationin the ultraviolet, x-ray, and gamma-ray regions, and study time variationsof these emissions.LAUNCH VEHICLE: Three-stage Delta, William R. Schindler,Goddard Space Flight Center, VehicleManager; Robert Gray, Head, Field Pro-

jects Branch, Goddard Space FlightCenter, Cape Canaveral, Florida.LAUNCH PLACE: Atlantic Missile Range, Cape Canaveral

Florida.NASA HEADQUARTERS

PROGRAM DIRECTION: OSO is part of the NASA's Office ofSpace Sciences Directed by Dr. HomerE. Newell. Dr. John P. Clark, Direc-tor of Geophysics and Astronomy Programs.Dr. Nancy Roman, Chief, Astronomy andSolar Physics. Irwin Cherrick, OSOProject Officer. Vincent Johnson,Delta launch vehicle manager.


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SPACECRAFT WEIGHT: 440 poundsEXPERIMENTS WEICX1T: 173 poundsPOINTING ACCURACY: One minute of arc (equivalent tosighting an 18-inch diameter objectone mile away)ORBITAL PERIOP,, v9 minutesINCLINATION: ' 33 degrees to the equatorORBIT: Circular, 300 nautical miles, plusor minus 50 milesLIFETIME: Estimated 6 monthsTRACKING ANDTELEMETERED DATAACQUISITION: NASA Goddard Space Flight Center'sMinitrack network


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- 2-1 -NASA TO LAUNCH OSO(ORBITING SOLAR OBSERVATORY)(S-16)

Man may soon get a new, undistorted look at the sun.In the next week or so, the National Aeronautics and SpaceAdministration plans to launch the first of a series ofOrbiting Solar Observatories from the Atlantic MissileRange. The OSO will be placed in orbit by a three-stageDelta rocket vehicle.First of the large "second generation" satellites,OSO is managed by and under the technical direction ofthe NASA Goddard Space Flight Center, Greenbelt, Maryland.The 440-pound OSO spacecraft has two sections, anoctagonal lower wheel on which is mounted a fixed iection.Each contains experiments. OSO and succeeding solar observ-atory satellites are regarded by many in the scientificcommunity as the most promising instrumentation advancein the study of the sun since development of the corona-graph 30 years ago. NASA hopes to use such spacecraftfor at least the next 11 years, (a full sunspot cycle)in order to study solar (minimum through maximum sunspot)activity.Such studies are vitally important because they mayhelp to unravel ;orne of the mysteries which have intriguedmankind since the beginning of time: how the Sun controlsthe upper atmosphere of the Earth and weather; the originand history of the solar system; and the structure andevolution of the stars and galaxies.In four years of space research, scientists havebeen studying the side effects of geophysical phenomena

dependent on the sun--the energetic particles in themagnetosphere, the ionosphere, and the structure andcomposition of th- upper atmosphere. OSO, however,seeks to learn ti. cause of these phenomena by studyingthe sun itself.The earth's blanketing veil of atmosphere is both ablessing and a hindrance to mankind. It stops the moredangerous space radiations. If it didn't, life as weknow it on earth would be considerably altered. Butwhile it protects life, it hinders scientific investi-gations on the origin and structure of our universe

because it filters out the sun's more interestingradiations.


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We only have two "windows" through which we can "see"the universe around us. The window most common to us isthat of visible light. The other "window" is the one ofradio waves which allows astronomers to pick up additionalenergies emitted from the sun and other stars. These twowindows make up only a small part of the electromagneticspectrum. Other radiations--gamma rays, x-rays, ultra-violet and infra-red--are absorbed or distorted by theearth's atmosphere. Only by getting above the atmospherecan we measure and observe these wavelengths.OSO, which may ze placed in a near circular orbitabout 30Ci aautical miles above the earth, will measure abroad range of electromagnetic radiation in the ultravioletx-ray and gamma ray regions with an array of 13 scientificexperiments. From these measurements the abundance of theelements i. n the sun, the sun's composition, and the inten-s'ty of its radiations can be studied.Maximum useful lifetime of the observatory is estimatedto be six months. The life span depends on the supply ofnitrogen gas used to align it with the sun. Its orbit will

be inclined 33 degrees to the equator. The NASA GoddardMinitrack network will track SO.One of several Goddard-designed instruments aboard isan x-ray spectrometer. Information from this instrumentcould lead to a theory for predicting when the sun is likelyto flare up and unleash deadly protons. These are the minutepositively charged constituents of all atoms which can occa-sionally reach energies of almost 50 billion electron voltsand can traverse the 93 million miles from the sun to earthin about 10 minutes.Only by kcnowing the "safe" flight periods, or byshielding the spacecraft can man and equipment be pro--tected from this radiation. NASA is pursuing researchin both areas.The University of Rochester experiment, one of 13aboard OSO, may tell us more about the thermonuclearprocesses that take place on the sun. The Universityof Rcchester experiment will measure gamma rays with anenergy greater than 100 million electron volts. Theserays could be caused by large solar flares. Otherexperiments include NASA Ames Research Center instru-mentation on ,;urface erosions of materials; Goddard'sinstrument to measure the energy of interplanetary dust


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particles hitting the spacecraft, and the University ofCalifornia's neutron, proton and electron detectors.Ball Brother. Research ccrporation of Boulder, Colo-rado, as prime contractor to NASA Goddard Space FlightCenter, produced the spacecraft w:rhich carries thesescientific instruments. The satellite must point atthe center of the sun with great accuracy so that thescientific instruments can "look" at the sun's radiations.

FLIGHT SEQUENCEThe OSO spacecraft will spin at 120 revolutions per

minute during the firing of the third stage of the Deltalaunch vehicle. At approximately 200 seconds after third-stage separation, gas Jets on the spacecraft arms willcause the vehicle to de-spin to 30 revolutions per minute.At this point, both the wheel section and the fan-shapedpointing section of the spacecraft will be rotating.Approximately 800 seconds after third-stage separation,the spacecraft's 3ail section is to lock on the centerof the sun.

The bottom portion of the satellite will continue tospin at 30 rpm to give the vehicle gyroscopic stability.A servo controlled motor driving against the wheel sectionwill keep the sail section and its scientific instrumentspointed toward the sun in azimuth. The second servo willprovide fine elevation control of the scientific instru-ments positioned in the central portion of the sail section.Both servos are controlled by photov.1tale sun sensorsmounted on the scientific instruments. Inenever thevehicle begins to precess, or turn away from the stun,nitrogen ga ? from a storage bottle will be releasedthrough nozzles to correct the satellites's position.The solar cell array consisting of 1860 solar cells onthe fan-shaped portion of the satellite provides all ofthe electrical power needed to operate the vehicle systems.During satellite "night," storage batteries will be used tooperate the necessary equipment. At the beginning of satel-lite "the day catching sequence" of acquiring the sun wli'be repeated.

Later orbiting solar observatories being developed oyNASA Goddard will be devised for even greater precision,perhaps with a pointingp accuracy of 5-]0 seconds of arc.These satellites may be able to scan for sunspots andthe sun's corcna.


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FACT SHEET ON DELTAThe Delta rocket used to launch OSO has launched sixNASA satellites: Echo I, Tiros II, III and IV, and Ex-plorer X and XII. The Delta has these characteristics:Height: 90 feetMax. Diameter: 8 feetLift-off Weight: A little less than 112,000 pounds

First Stage (Modified Douglas Thor):Fuel: Liquid (LOX and kerosene)Thrust: About 150,000 potndsBurning Time: 160 seconds

Second Stage (Aerojet General):Fuel: LiquidThrust: About 7,500 poundsBurning Time: 109 seconds

Third Stage (Allegany Ballistics Laboratory X-248):Fuel: SolidThrust: About 3,000 poundsBurning Time: 40 seconds (After 7 minute coast)

Firing Sequence:The first stage falls away on burnout. The secondstage ignites immediately. The nose fairing which coversthird stage and payload is Jettisoned after twenty secondsof second stage burning. The third stage doesn't igniteuntil seven minutes of coasting after seconds stage burnout.

Then, the third stage is spin stabilized and the second stagefalls away. The third stage reaches an orbital velocity ofalmost 17,000 miles per hour.


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SPACECkAFT DESCRIPTION

Orbiting Solar Observatory is designed primarily asa stabilized platform for solar-oriented scientific instru-ments. In addition, experiments that do not require fixedo:ientatior, with respect to the sun are housed in the spin-ning wheel section of the spacecraft. Electrical power forthe vehicle is supplied by an array of 1860 solar cellsmounted on the stabilized section. A complete telemetryand command system is provided to transmit informationback to earth.The spacecraft has two main sections. The lower wheel-like structure is composed of nine wedge-shaped compartments.Five of these compartments are used for scientific experiments;the other four are used to house some of the electronic con-trols, batteries, and all of the telemetry system, radiocommand system, and the in-flight data storage system.Three spheres on extended arms hold pressurized (3,000 PSI)nitrogen gas for the spin control system.The top part of the spacecraft is a stabilized sectionmounted on the wheel. The fan-shaped array to which siliconsolar cells are attached comprises the larger part of the

structure.The two main structures are connected by an aluminumshaft that runs from the base of the instrument--solar cellassembly through the center of the wheel and ends in thesupport ring structure on the underside of the wheel. Thisshaft is held in position by two bearings, one at the topof the wheel and one at the bot;om.Mounted on the shaft between the bearings is a highpressure (3,000 PSI) tank which carries the nitrogen gassupply for precession Jets mounted on top of the solarcell structure. A torque motor, mounted on the base ofthe shaft, drives the shaft relative to the wheel. Thismotor actively controls the azimuth orientation of thestabilized section of the spacecraft by driving at anequal but opposite rate to that of the wheel. Also mountedon the base of the shaft is a slip ring assembly that allowspower, telemetry signals, and control signals to be trans-mitted from the stabilized section into the spinning wheel.030 was designed for maximum utilization of the payloadsection of the Delta launch vehicle. The wheel diameter of44 inches is the maximum diameter allowed by the Delta shroud.During launch the three nitrogen gas cortainers on the ex-tended arms are folded down around the third stage motor.

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After payload separation, the nitrogen tanks are extendedoutward, and the diameter of the payload is increased to92 inches. Since these spheres are carried at the ends ofthe long arus, the axial moment of inertia of the spacecraft1.s increased, thus assuring that this moment of inertia isconsiderably larger than either transverse moment of inertia.The over-all height of the satellite is 37 inches.030 utllizes the gyroscopic properties of a spinningbody for stabillty. Prior to third staae. firing, the entirethird stage is spun up to approximately 120 rpm by a systemof small rocket motors. Af1er third stage burnout, the armsnupporting the three gas -coj4ainer'f are extended. The

Satellite is separated ftromh the spin rate ofthe wheel is reduced to approximately 30 rpm by Jet action.This spin rate is maintained with i 5 per cent of nominalvalue by gas Jets attached to each of the spherical gas con-tainers which supply them. The Jets are actuated by a signalfrom an electronic control system that computes the instan-teneous period of rotation of the wheel with reference tothe sun. The three gas-filled spheres are interconnectedto assure that unbalance of the rotating body does not occurdue to an unequal gas flow rate through the Jets.The unique biaxial pointing control system of 030utilizes the entire vehicle as part of the controlled plat-form. Coarse elevation control of the stabilised seetion isaccomplished by controlling vehicle attitude with on-off Jets.(This is possible because of the gyroscopic properties of thespinning body.)By exhausting high pressure nitrogen gas throughnozzles mounted on the stabilized section, torques of eithersense acting along the line of sight can be produced which precessthe spacecraft in elevation. This active control of the space-craft's spin axis is used during initial acquisition and, sub-sequently, to counter the effect of external torques actingupon the satellite. The control system used to actuate the

precession Jets on OSO maintains the spin axis perpendicu-lar to the solar vector within about 3 degrees. No controlabout the sun vector (roll) is provided, but rates aroundthis axis are very slow due to rigidity of the gyro.Azimuth and fine elevation poaitioning of the instr-uments is accompliihed by electrical servo motor control.

Thci elevation servo motor is mounted on the casting thatRupports the pointed instruments. Ths motor drives theInstruments relative to the solar cell array or sail sectionfor fine positioning in elevation.The azimuth and elevation servo motors are actuatedby signals from photodetectors mounted on the stabilized

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wheel to provide a nearly constant voltage supply at alltimes, The cell array is always normal to the sun vectorwithin 3 degrees.The total surface area of the array is 3.72 square feet.The ar-ray is composed of thirty-one 18-volt modules of 60 cellseacn producing a power output of about 27 watts. The averagepower available for use from the nickel-cadmium storagebatteries is about 16 watts. Since the telemetry, data system,and control system require approximately 7 watts, 9 watts areavailable to the various scientific experiments.080 telemetry is accomplished by an FM-FM system.Eight non-standard low frequency subcarriers are multiplexedinto a tape recorder. The tape recorder, running at approx-imately 0.75 ips, records the complex signal for 90 minutesof the 95-minute orbit. During a 5-minute interval in whichthe satellite is within receiving range of a ground receivingstation, the tape recorder plays back the recorded complexsignal at 18.35 times the record speed. At this playbackSpeed, the suboarrier frequencies become standard IRIGfrequencies and modulate the spacecraft trarnsmitter. Thereare two independert parallel multiplexing systems. Eachsystem has a set of subcarriers, a tape recorder and a

transmitter.The tape recorder is a continuous loop device thatrecords continously until commanded toy play back. Its play-back interval is timed to allow the entire tape loop to passover the playback head. It then reverts to the record stateautomatically.One subcarrier is provided by a fixed frequency, highlystable oscillator. This frequency is used in the tape speedcompensation networks of the receiving station to compensatefor permanent changes in tape recorder speed and for transient

changes such as wow and flutter up to 300 Cps.The subcarriers are recorded and played back at equalamplitudes. A pre-emphasis filter precedes the transmitterinput to provide the amplitude taper which is commensuratewith transaitter Pnise level and a bandwidth of 100 kc.The transmitter consists of twp parts, the modulateddriver and the r.f. power amplifier. Both units use solidstate active elements.During the 90-minute record phase of the orbit, thedriver power to the r.f. amplifier is reduced to permit anoutput of 300 mw. By ground control the driving signal tothe power aaplifler is increased permitting an output of1,75 watts during the 15 minute tape recorder playbackinterval. Since only one transmitter is on at a time, both )may operate at the same frequency.

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The antenna system incorporates the use of two ofthe spacecraft arm supporting structures as radiatingelements. The structure of the third arm is excited onlyduring the countdown and launch phoes and becomes aparasitic element when the spacecraft is in orbit. Antennapolarization requires diversity combining of linear andhorizontal polarizations. Due to a 2 db loss in the antennasystem, the radiated power will be in the order of 1.0 watt.The command system for OSO is a 7-tone AM system.With these 'r tones, the following functions can be performed:Comimand No. 1 Playback "ON"Command No. 2 Playback "OFF"Actuated automatically bythe tape recorder or manually.Command Nos. 3 and 4 Transmitter selectCommand Nos. 5 and 6 Multiplex system selectCommand No. 7 Wheel experiments "ON"Command No. 8 Wheel experiments "OFF"Command No. 9 Pointed experiments "ON"Command No. 10 Pointed experiments "OFF"

Test ProgramA special environmental test program was developed atBall Brothers under the direction of GSFC to check out the030 spacecraft under simulated flight conditions. It beganby an extremely precise balancing of the rotating structure

of the spacecraft. Next, the prototype was subjected to aseries of vibration tests.A vibration table with a 7,500-pound force output wasused. Random noise testing, and sine wave testing wereaccomplished. Vibration in three axes simulated the Deltarocket boost portion of the spacecraft flight. After theseruns, the satellite was placed on a balancing table forcalibration and checkout of the instruments and the space-craft system. The spacecraft was then placed in a 10' x 15'thermal-vacuym chamber which attained a vacuum of betterthan 5 x 10-( mm Hg, or approximately 1 billionth of thepressure at sea level. The prototype was tested for twoweeks of continuous operation in the chamber.A series of mirrors outside of the chamber were usedto direct an artificial sun source into the chamber. Insidethe chamber, after the initial orbital acquisition sequence

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was run, the spacecraft spin rate was reduced to 30 rpm.When the signal was given for the spacecraft to acquirethe sun (simulating the 4aytime portion of the orbit),Jthe pointing seclion of the spacecraft detected theartificial sun source and began to de-spin. Within 45seconds the pointing section was lookin at the center ofthe sun source. After a series of "day and "night" se-quences inside the chamber at high and low temperatures,the prototype was then placed on the table again to de-termine where and if "outgassing" or evaporation ofmaterials under the high-vacuum condition inside thechamber had affected the balance of the satellite. Aftereach test, complete calibration and checkout tests wereperformed.In December 1961, a structural model with a com-plete communication system was sent to NASA's Fort Myers,Florida Minitrack Station where it was hoisted by helicopterto 5,000 feet and flown over the receiving station. Thetelemetry and command systems were checked out to assurethat the spacecraft signals were received and interpretedproperly by the ground equipment.Much emphasis has been placed on component testingto assure that every component part and subsystem functionsperfectly, Some of the most critical satellite componentswere placed in a 14-inch bell Jar vacuum system which hasthe capability of reaching vacuums of 6 x l0- mm Hg. Itwas in this chamber that the first tests on a Ball Bros.Research Corp., developed lubricant to permit slip rings,bearings and brushes to work under high vacuum, were run.The new lubricant reduces the adhesive and cohesive forcesby imparting an artificial two-dimensional atmosphere onmoving surfaces. Slip rings treated with the lubricant hareoperated under high-vacuum conditions (3 x 10-d to 4 x lo-9mm Hg) as long as 1,300 hours and 107 revolutions. Motorsand bearings have operated even longer.Pre-launch tests on some of the experiments weremade using sounding rockets. On September 30, at NASAWallops Station in Virginia, the Ball Brother's solarpointing control and the Goddard solar x-ray spectro-photometer were successfully tested in a high altituderocket launch. The Aerobee rocket reached an altitudeof 140 miles and pointed at the center of the sun for328 seconds at better than / 1 minute in elevation and/ 3 minutes in azimut.The S0O flight model has undergone the same test as

the prototype model except that vibration testing levelswere reduced to simulate more precisely the Delta rocketlaunch sequence.4 - 6


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- 5-1 -ORBITTNG SOLAR OBSERVATORY - EXPERIMENTS

There are 13 scientific experiments on board OSO, first ofa series which will study the sun over at least one solar cycle.These experiments are housed in the rotating wheel and in thesun-oriented section of the satellite. Wheel experimentsgenerally are sky-mapping experiments comparing radiation fromthe sun to that in other portions of the sky. These experi-ments flash by the sun once every two seconds, due to therotation of the wheel, but always pass within a few degreesof the sun due to the control of the orientation of the spinaxis of the spacecraft. The oriented experiments, however,are continuously pointed at the center of the sun to an accuracyof about a minute of arc. This is equivalent to aiming at an18-inch beachball one mile away.

POINTED EXPERIMENTSSolar X-ray Ex eriment (10 to 400 Angstroms) (X-ray Spectrometer),-,WiiaBhring and Dr. Werne-rM. Neupert, NAA Goddard SpaceFlight Center, Greenbe t, Maryland.

Solar x-rays shape some ofthe najor features of the ionosphere.Sporadic, explosive outbursts of x.-rays are synchronized withsolar flares. The stormy character of solar x-ray Emissions farexceeds that of any portion of the ultraviolet or visible spectrumand are only matched by the violent outbursts observed at theradio frequency portion of the electromagnetic spectrum. Probablythe source of solar x-ray emission lies within the corona verynear its base where the temperature is on the order of 1,500,00 F.Very soft x-rays (10 to 100 Angstroms) cannot penetrate to

less than 65 miles above the ground. Harder x-rays (1 to 10Angstroms) reach progressively deeper levels down to the bottom-most fringe of the ionosphere. At still shorter wavelengths,x-rays have been observed with balloon-borne instruments.Our knowledge of the x-ray region is as yet confined to thebroadest features which vwe have discerned with rocket measure-ments (that go back to the days when the German V-2's were usedat White Sands); balloon flights, and data gathered from theU.S. Naval Research Laboratory's satellite Solar Radiation 1(1960 Eta 2), which measured x-rays from 2 to 8 Angstroms. Highresolution x-ray spectra still remain to be achieved. Hence,this experiment on OSO ., which will measure from 10 to 400Angstroms. (An angstrom is the unit of measurement of thelength of a wave of light. It is one ten-millionth of a millimeter.) The visible range of light runs from wave lengtheof7,600 Pngstroms (red) to 3,900 Angstroms (violet), only a minutepart of the electromagnetic spectrum.


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5-2 -A study of the x-ray radiation coming from a quiet sun couldlead to a theory for predicting solar flares and also make itpossible to better simulate the sun in earth-bound environmentalchambers.The solar x-ray spectrometer is mounted in an instrumenthousing in the sail, or non-spinning portion of the spacecraft.Direct solar radiation enters a tiny entrance slit and strikesa rounded.grating, that is flely ruled (576 lines per mm) whichdisperses this.radiation into its characteristic x-ray image. Itis then focused along A circle according to wave length. Adetector is motor-driven along a track coinciding with this circle

and measures the x-ray intensity at various wave lengths.The pulse output of the detector is amplified and convertedinto binary wave forms which are then coded and sent back toearth by the spacecraft telemetry.

0.510 Hev Gamma-RaY Monitoring Experiment, Kenneth Frost andWillIamaWhite. NA3A Oodaard Spaoe Filght center.Gamma rays or "photons" have energies of about one millionelectron volts and are similar to light rays of x-rays in thatthey travel with the same speed and are not deflected by

electric and magnetic fields. Unlike true cosmic rays, but likestarlight, the gamma-rays arrive from the Lame direction in spaceas they originated. They cannot, however, penetrate the earth'satmosphereGamua-rays are born in the interaction of atomic nuclei inor near starse Since the sun itself is a giant atomic furnace,0S0 -. should observe gazma-rays emanating from the solar surface.Prom the intensity of these rays we should learn more about thethermonuclear processes responsible for the sun's heat and lightwhich are needed for maintaining our life on earth.The 0.510 Mo e Gamma-ray Monitoring Experiment utilizes twodevices which supplement each otherin order to register thelight flashes in this energy range,. They are a. cintillator anda photomultiplier tube, The 0.510.mev spectral line is theeloctron-positron annihilation line where gamma-rays are generatedby the 100 percent conversion of the mass of these particles(electroh-positron) into energy,Pulse signals from the photomultiplier are fed into amanyochanneled analyzer where they are coded and fed Into thetelemetry tape recorder whichocan be commanded on by earthstations to play back the data.The only difference between this experiment in the sail sectionand the gamma-ray experiment in the wheel section of the space-craft is that this one looks at the sun continuously and theenergy analysis should be Improved. )


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-5-3-20 to 100 Kev x-ray Monitoring Experiment, William White and(neth Frost, NASA Goddard Space Flight Center.r

This experiment has a detector exactly like the scintillatorused for gamma-ray experiments, except it has a thinner crystal.X-ray emissions in this range are believed to be associatedwith the changes in frequencies of certain solar radio events.It may be possible to compare the intensity variation of thesex-rays with the same emissions recorded by radio observatorieshere on earth.1 to 8 Angstrom X-ray Monitoring Experiment William White,Kennth Frost,_and Robert Young, NASA Godda- Sp light Center

Two ion chambers will be used in combination, to get thewave length discrimination, to monitor the solar output inthis energy range. They consist of a thin beryllium windowsurrounded by Xenon gas. Monitoring of this region willsupplement information obtained from the x-ray spectrometeralso mounted in the pointed section. This will be particularlynecessary during a solar flare when x-ray emission is increasedwith the resultant hardening, i.e. shift to shorter wave lengthsof the spectrum and an increase-In intensity.Dust Particle Experiment, Merle Alexander and Curtis McCrackenNASA Godda-rdd Space Fit;ht Cehnter

This experiment will measure the incoming rate, momentaand kinetic energies of microscopic dust particles. A photo-multiplier tube, or register, for light emissions, is coatedwith a very thin layer of aluminum. The photomultiplier tubemeasures the luminous energy formed when a dust particle hitathe aluminum coating. A microphone on the tube will measurethe mechanical impulse delivered by the impacting particle..This data will be coded into proper form and then stored onthe spacecraft tape recorder for telemetry to the gound.WHEEL EXPERIMENTSSolar RadiationE xe MOOt(380o 4,800Angatroms, r.Knneth

L. Hallam, Harold Murphy, and William Wh ite, NASA Goddard SpaceFlight CenterA special photodiode with a filter will be used to restztotthe light received to those in.the 3,800-4,800 Angstrom range.(This is the blue range in the visible light spectrum.) Thiswavelength region encompasses the frequency of maximum:flux(output) from the sun. Knowledge of this region is important

in determining the total energy balance of the sun, or howmillions of tons of hydrogen are converted into helium with thespillover being transferred to the solar system in the form ofheat and light. This instrument should be able to determinevariations-of the solar output as small as 0.1 percent.


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- 5-4 -Solar Ultraviolet (1,100 to 1,250 Angstroms), Dr. Kenneth L.Hallam, Robert Yourg, and William White, NASA Goddard Space FlightCenter.

Again, an ion chamber will be used to monitor this u-vrange whose wavelength region includes the Lyman-Alphachromospheric emission, most fundamental line of hydrogenspectrum. Measurementsof this line are important. in determiningwhether the emission line remains the same during active andquiet solar periods.Solar Gazmma Rays Experiment (0.2 Mev to 1.5 Mev) (High EnergyDistribution)., William White Kenneth Frost, and Dr. KennethHallam NASA (oadard space Flight Center

This experiment is essentially the same as the gamma-rayexperiment carried in the pointed section of the spacecraft. Onedeteztor is shielded to get a view angle of 20 degrees. Thesecond detector is unshielded and is used to determine whetherany radiations have been generated within the satellite because ofenergetic particles encountered in space.Solar Gamma-Ray Experiment (50 Key to 3 ev Low Energy Dis-tr ~ufonj Dr jon ft Wiker and D. M. P._eterson, Uni~versityof Minnesota.

Measurements of gamma-rays are complicated by the large"background" due to cosmic rays and the weak intensity to bemeasured. The intensity is less than one gamma-ray crossinga 1-centimeter-square area each second. A special detector,known as a "Compton telescope," and special circiuts have beendeveloped as the University of Minnesota to perform thismeasurement in the 50 Key to 3 Mev range.The telescope is mounted in the wheel of the satellite andscans the sky as the wheel rotates, continuously recording andstoring information about gamma-rays. The entire instrumentweighs only 30 pounds, and has a volume of less than one-halfcubic foot. It has nearly 400 transistors and operates con-tinuously on only one-half watt of power.

Neutron Monitor Exeriment, Dr. Wilmont Hess, University ofCTalifornia tDr. Hess now is associated7 with the NASA ddir-d SpaceThis neutron experiment will be the first major neutronexperiment to be made in space. The neutrons that OSO will countin its low orbit will be predominantly from the earth. Theoretical-ly , we think we understand these neutrons. They leak out of theatmosphere of the earth. They are produced in the atmosphere.bycosmic rays striking oxygen and nitrogen nuclei. (


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-5-5-Previous rocket experiments have given us reasonable

measurements Of the neutron flux in space for short periods oftime. The values obtained were different, but one flightwas during a solar storm so the difference is probably notsurprising. OSO's flight will give a measurement of the neutronoutput in space for an extended period of time. From this wehope to be able to measure the time variations of the output,and hopefully,, w~etill be able to study the neutron enhancementeffects during a solar storm.

Besides measuring the qu'et day neutron flux and its timevariations, OSO .iill loot for f'lux. variations at sunset to seeif an eLfect can be observed related to solar neutrons or x-rays.Understanding the quality and quantity of neutron flux in,apace is important in igself, but it is also important becausethe decay of these neutrons forms one of the important sources ofthe Van Allen radiation belt, or magnetosphere.

Lower Van Allen Belt Studies, Dr. S. Bloom, University of California4 This proton-electron experiment consists chiefly of adetector for distinguishing between electron ionization eventsand proton (and other heavy particles) ionization events. This

e;xpjei'inent was chosen because i', s expected that the largestfraction of high-energy radaiaticn will be among these types.A newscintillator detector har been developed which employsElectronic means MFor distinguizsing between proton and electronionization events in thle samic scintillator. By this technique,maximum functionS are comprre,,;ed into as few! lectronic circuitsas 0ossible.

Emissivity otability of Surfaces in a Vacuum Environment Experi-menit, Dr. G. G. Robinson, HA11L Ame- I"esearch CenterDuring flight through space, spacecraft must rely entirelyupon thermal radiation to gain or lose heat to their surround-ings. An important consideration in design of spacecraft isthe type of radiation surface used for temperature control.For example, although most polished metal surfaces reflecta large part of the sun's rays, they give up the heat they doabsorb at only a very low rate, and consequently reach hightemperatures in the sun. White paints and enamels, on theothe, iandc, while also reflecting most of the incident sun-light, emit heat at a high rate, which causes them to operate atlow temperatures.


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- 5-6 -Stability of the thermal characteristics of temperature-control surfaces such as these is very important in the space-craft design. Flight in the space environment, however, cancause changes in the radiation properties of surfaces, leadingto inadequate temperature control. The magnitude and rate ofsuch changes is at present not known for most materials.Ames has developed an experimental package for OSO toperform theaw tests. The experiment consists of measuringthe temperature of several test surfaces during exposure to

conditions in space. From changes in the temperature of thesurfaces with time, it will be possible to determine theamount and rate of change in the thermal radiation character-'.%tics of the surfaces.Solar Gamma Rays Experiment (100 Mev-500 Mev) (High EnergyDistribution), University of RoChester, Drs. M. Saveaorr andG. Fazio

The primary objective of this experiment is the detectionof high-energy gamma-rays originating in solar flares; secondaryobjective is to monitor gamma radiation from the quiet sun andfrom other regions of the sky.

The gamma-ray is converted into an electron-positron pairin a lead sheet. The pair generates Cerenkov light in aplastic cylinder which is detected by a photomultiplier opticallycoupled to the plastic. As protection against primary relativ-istic charges particles, an anticoincidence scintillator isplaced between the lead sheet and the Cerenkov cylinder,The rays so detected are counted for various sectioridf skyas satellite wheel sweeps the circle.


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BACKGROUND INFORMATION ON, HE SUN

In the 350 years since Galileo made the earl4 est physicalobservations of the sun by telescope, important advances inknowledge of the sun have not occurred at a uniform rate, butusually have been made in clusters shortly after the develop-ment of new types of instrumentation or new physical principles.Jan Lippershey's telescope brought the area of visualobservations that lasted for 250 years. This was followed byother instrument advances, among them: the spectroscope, thespectroheliograph, the coronagraph, time-lapse photography,observation of radio emission observation of the ultravioletsolar spectrtu from rockets, and the neutron mohitor andparticle detectors. These instrumentation advances almostconcurrently were aided by intensive theoretical-interpretations.Today, solar physics research seems to stand at the thres-hold of a Golden Age. With the Orbiting Solar Observatory, newinstruments will be placed above the earth's blanketing veil ofatmosphere and will be able to make direct measurements of thesun with a clarity not possible before. Why does man want todo this? For scientific reasons -- valid in themselves --mankind has been investigating the sun as a typical star ini connection with the study of stellar evolution, and as thecentral body of the solar system to determine how it affectslife on earth.While our knowledge of the sun has increased greatlyover the years, many of the most conspicuous operations ofthe sun -- which is estimated to be 5-10 billion years old --remain shrouded in mystery. Galactic cosmic radiations havebeen recognized and studied for years. However, the abilityof the sun to produce bursts of energetic particles was dis-covered only in 1946, and solar cosmic radiation has beeninvestigated in detail only since 1956 -- a year before spaceflight with an artificial earth satellite.


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- 6-2 -In the 20 years before the large solar cosmic ray ient ofFebruary 23, 1956, there were only four cases of an increasein cosmic ray intensity, measurable on the earth by ionization-type detectors, that were related to activity on the sun. Smallwonder that the idea became widespread that these events werequite rare.The introduction of the neutron monitor in 195( improvedthe sensitivity of earth-level measurements, but the realbreakthrough came only recently with the use of particle measure-

ment devices sent into space.Cosmic ray particles ejected from the sun are known to bemostly protons with energies ranging from less than 10 MEV(million electron volts) to those which may occasionally reachLOo MEV. These nuclei of hydrogen can traverse the 93 millionmiles from the sun to the earth in less than an hour, the timebeing dependent on the energy in question.These solar proton events--particularly the larger ones--present a definite hazard to manned space flight; a hazardwhich can be coped with in only two ways: establishment of,areliable prediction system as to when solar flares are likelyto occur, and/or shielding spacecraft from these radiations.At present, the National Aeronautics and Space Administrationis vigorously pursuing both research areas.It is known that solar cosmic rays detected near the earthoriginate in connection with large flares above the visibledisk or photosphere of the sun. Flares are sudden increasesin intensity of radiation that occur over large areas in thesolar atmosphere. They are usually observed in the light ofhydrogen-alpha, a red hydrogen line at 6563 Angstroms. Aflare is not a separate and distinct event, but only a symptom"of something much more basic that is going on in the sun. Un-

fortunately, our understanding of the total phenomenon is veryincomplete. However, we do know that --with very few ex-ceptions--flares originate in active regions, or centers, onthe sun.The sun has a diameter of about 864,000 miles and isabout 93 million miles from earth. It is believed to be oneand one-half times as dense as water. The center of the sunhas a temperature of 35 million degrees Fahrenheit and a pressureof almost a billion atmospheres. The energy created in the coreby thermonuclear reactions passes outwards until it zets to thephotosphere, a very thin radiating layer only about b2 miles

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- 6-3 -deep. This gives the sun its apparent sharp outline. At thephotosphere, the temperature has decreased to 10,000 degrees.

The chromosphere is the transition layer of the solaratmosphere, about 9,300 miles thick, in which the temperatureincreases from the 10,0000 temperature of 'he photosphere tothe million degree temperature of the corona, or outer atmos-phere. Here the density and pressure also fall off sharply.Visible to the naked eye only at times of solar eclipse, thechromosphere appears to be a pinkish-violet layer. The greatflame-like masses which proJect above its general level arexnown as prominences.

The chromosphere merges into the corona which is the *x-tremely hot, tenuous envelope around the sun. The corona hasno sharp outer limit, and its pearl-like light may, in fact,extend out several million miles.The photosphere, or visible surface of the aun, appearstc be bubbling rice-like granules. Each of the granulations isa convection cell with an average liftetime of only a fewminutes and a diameter of about 500 miles. unspots are thedark visible manifestations of an active region in the photo..

sphere. The dark central portion of a sunspot is called theumbra. The grayish, filament-like structures, some 180 milesthick at the most, around the umbrae are called the pemwbrao.These filaments have an average lifetime of about one-half hour.Sun spots are known to vary in area from a hundred milesin diameter to enormous spots over 150,000 miles in diameter.Large sun spot groups differ from each other in form, behavior,and lifetime. However, some generalities can be made.

A typical large group first appears as a pair of smallapots about three degrees apart in longitude and at a latitude0 5 degrees to 40 degrees north or south of the solar *quator,depending on the level of solar activity at the time. Thespots grow rapidly and begin to separate somewhat in longi-tude. -Small spots begin to appear around and between the twolarger one. Finally, when maximum size is eaohed, the spotsare about 10 degrees apart. After a few dys or more, thesize decreases and the spots disappear. dull sun spotsusually last only a few days. Large spots last a few weeks,but some persist for several months or more. 'The rate of de-velopment of a sun spot group is fast during Its early lifebut decreases as the maiimam size is reabohj.

Although tho general magnetic field of the sun is quiteweak, sunspots have been found to con3tain vory strong fields ofthe order of several thousand gausp.C'\


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-6-4Photograpi's showing phenomena of the chromosphere arecalled spectrohelio'rams because they are made with spectro-heliographs or special filters which isolate the monochromaticradiations of the chromosphere -- either the H-alpha line(a hydrogen line at the red end of the spectrum 6560A0 ) or theK-line of ionized calcium (violet in color, approximately 3900A0).Spectroheliograms taken in light of ionized calcium showmany bright patches which are called plages. It is apparentthat plages tend to cluster in the two sunspot belts, one northand the other south of the solar equator. A plage is one of

the most long-lived manifestations of solar activity. It ap-pears at least several days before its associated sunspot groupand may outlast it for a year or more, although most do not.A flare is observed as a sudden increase in radiationintensity in part of a plage. When these active regions areobserved in the light of H-alpha, we see patterns similar tothose of iron filings around a magnet. This suggests +hepresence of strong magnetic fields extending from the sunspotup through the chromosphere. Large flares usually have afilamentary appearance, while small ones are more likely tolook like patches or blobs.Solar proton bursts generally occur in connection with solarflares. Since there is no reliable method so far developed fortelling whether an active region will produce a cosmic rayflare, NASA--in support of its manned space flight program, willeither have to predict when large flares are likely to occur orgo to extensive shielding of spacecraft equipment and person-nel.However, there are certain features observed on the sunthat tend to be present during times of solar activity. Largeflares are Just one manifestation. Other features are calledflare indicators. Examples are:1. Large, complex spot group2. Complex magnetic field in a sunspot group, with manypoles of opposite sigu.3. Unusually bright plages.4. Frequent bursts of radio emission and a high levelof solar radio noise.5. Hot spots in the corona, indicated by the appearanceof the yellow line of Calcium 15 at the limb, or edge

of the visi;ble disk. ()


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-6-5-6. High level of activity in any active region that inindicated by many small flares, and the presence ofcertain types of prominences.When none of these indicators is present, a "safe period"can be predicted with fair accuracy. However, when a "danger"period is forecast on the basis of the presence of any one ofthe flare indicators, in most cases it happens that a large flarenever occurs. While this overcaution can be tolerated duringminima in the 11-year cycle of solar activity, such as the onewe are approaching now, a level will be reached, probably inlate 1966 or early 1967 (the next maximum of solar activity)when there will be no predicted "safe periods."One of the major tasks confronting NASA is to refineprediction methods so that "danger periods" will be shorter,and "safe periods" longer and also more reliable. Statisticalwork in establishing an operational solar flare predictioncapability in support of manned space flight in now being under-taken at the Goddard Space Flight Center, Greenbelt, Maryland.


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SOLAR GLOSSARY

Age: Estimated 10 billioon yearsDiameter: About 864,000 (109 times that of Earth).Volumes 1,300,000 times that of Earth.Density: 0.26Mass: 333,000 x EarthDistance from Earth: 93 million miles or 1 Astronomical Unit.Specific Gravity: 1.41 (Earth, 5.52)Surface Gravity: 28 (Earth, 1)Velocity of Escape: 383 miles a second (Earth, 6.95 milesa second)Surface Temperature: 10,3000F (Earth, average of 320F)Interior Temperature: 35 to 50 million degrees P. (Earth, 50000F)Rotation: Varies, more rapid near the equator whereaverage is 24.65 days.Sun's Antapex: The point in space from which the sun ismoving. (Generally believed to be theconstellation of Columba;)'Photosphere: The visible disk of the sun, diameter 1/20.Chromosphere: The rosy red (light pinkish) layer, oratmosphere which extends out severalthousand miles. Visible only duringsolar eclipse because it is overwhelmedby the photosphere's brilliance, Usuallyobserved through a spectro-helioscope.Corona: The sun's outermost layer visible onlythrough a coronograph or total solareclipse when it appears as a varyingwhite halo against the dark silhouette

of the moon. When there are relativelyfew sunspots, the corona has an almostsmooth outline. During disturbanceshowever, its streamers can extend out-ward for millions of miles.7-1


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,* S *^

Prominences: Geysers of bright hydrogen that compe upfrom the surface, or photosphere. Flame-like in appearance they sometimes shootoutward a million miles. The morespectacular seem to be associated withsunspots.Spicules: The fine structure in the corona seen atthe poles. Has life-time measured inseconds.Sunspots: The dark areas in the photoophere havingextremely strong magnetic fields, Ap-parently they are the venting valve forthe tremendous forces at work below thephotosphere. Some of the larger oneshave a total area of several million miles.Temperature within a sunspot is believedto be several thousand degrees less thanthat at the surface. The number of sun-spots varies over a solar cycle of 11.3years between maximum and minimum sun-spot activity.Gauss: A measurement of the strength Of a magneticfield. The magnetic fiel4 Of sunspotlsometimes reaches 3,000 gauss.Flocculi: The bright or dark calcium clouds that arefound near sunspots. Sometimes calledplages. The general form for anychromospheric turbine.Granulations: Usually elliptical in shape and resembling

grains of rice, they appear over the entiresurface of the sun. Constantly in motion,they have a turbulent life of only a ?ewminutes before they die and are replacedby new grandes..Limb: The edge of the sunts disk, darker thanthe center of the disk.Gegenschein: The counter glow or faint reflection ofsunlight from dust-size meteoroids inspace.Cosmic ray particles: Mostly protons with energies ranging fromless than 10 MEV (million electron volts)to 50 BEV (billion electron volts). (

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Umbra: The dark central portion of a sunspotPenumbra: The grayish-filament-like structuressurrounding the umbra.Solar constant: A figure which represents the rate ofenergy received from the sun. Figuredas the amount of energy received on thesurface of a hypothetical sphere outsidethe earth's atmosphere. Solar constantis 1.94 calories per square centimeter.Cosmic year: The period of time, about 200 millionEarth years, required for the sun to becarried completely around the center ofthe Milky Way galaxy by the rotation ofthe galaxy. Our sun is Just now reachingvoting age, of 21 cosmic years.Carbon cycle: A process which produces the energy instare, in which millions of tons ofhydrogen are transformed into millionsof tons of helium with only a few

million tons converted into energy.Proton-Prpton Cycle: The process of creating stellar energy ata lower temperature than that requiredfor the carbon cycle. Probably the mostimportant energy source in the Sun.Gamma Ray: A quantum of electromagnetic radiationemitted by a nucleus as a result of aquantum transition between two energylevels of the nucleus. Energies rangefrom 100,000 to 1 million electron volts.Ultra-Violet: A range of radiation of frequencies nexthigher than those of visible light.Spectrometer: An instrument which measures intensityin various wave lengths. A dispursingelement, such as a diffraction-gratingis employed to give the various wavelengths.

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orbiting solar observatory s-16 press kit

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