nimbus a press kit

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NATIONAL AERONAUTICS AND SPACE ADMINISTRATION TELS WO 2-4155E, WASHINGTON, D.C. 20546 *WO 3-6925

> FOR RELEASE: SUNDAYAugust

9, 1964*RELEASE NO: 64-195

NIMBUS WEATHER

SATELLITE SCHEDULED

FOR LAUNCH

The largest experimental weather satellite ever built by the

United States is scheduled for its maiden flight by the National

Aeronautics and Space Administration from the Pacific Missile Range

in California no earlier than August 14.



-2- Q

Eva1hat.v '.- AdvaXncd Vidicon Camera System (AVCS) for

tapa storare and readout of global cloud pictures during

daylight.

Provide improved Dictures of local clouds by means of the

Nimbus Automatic Picture Transmission (APT) system.

Evaluate the High Resolution Infrared Radiometer (HRIR)

system to map global night-time cloud cover.

The stabilization system, to orient the spacecraft sensors for

viewing the Earth vertically, the power system to operate the instru-



- - ' - - --

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This control system -- plus a near-polar orbit -- permits

Nimbus to look at Earth's entire 200 million square-mile-area

every day,

If the Thor-Agena-B launch vehicle successfully places Nimbus

into orb.t, the cameras and the infrared sensors in the satellite

will view the Earth from some 575-statute miles high, providing

continuous cloud pictures during each 14-orbit day.

In contrast, the spin-stabilized TIROS satellites view about 20-

25 per cent of the Earth each day.



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The Infrared ra.La tIon is modulated and recorded on a tape

recorder and then transmitted to a ground station. A facsimile system

reconstitutes the pictures and provides a cloud picture with a

resolution of five miles. The cloud pictures will be of a quality

comparable to present TIROS pictures.

The Automatic Picture Transmission (APT) system was designed

for Nimbus and successfully tested on TIROS VIII last December. It

takes real-time pictures which are'sent immediately to relatively

simple APT ground stations scattered around the globe. The camera



O-5--

AVCS pictures can be transmitted directly to one of two Command

and Data Acquisition (CDA) stations, when the satellite is within

line-of-sight-range of the station. Pictures taken of other parts of

the Earth are stored on a tape recorder and will be transmitted on

command.

CDA stations are at Gilmore Creek, Alaska and Rosman, N.C. Both

of the stations use 85-foot diameter antennas to receive weather data.

The Alaskan station will acquire the spacecraft an average of 10 of

the 14 orbits each day. The North Carolina station will acquire an

average of two orbits a day of the four missed on the Alaskan station.



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Pictures from :um.bus al11 not be transmitted until it has been

determined that all spacecraft subsystems are working properly. The

operational plan is to turn on eacn system in a series of steps,

and then command the satellite to start taking pictures.

If the spacecraft performs as planned the first APT pictures

will be taken and read-out at Goddard at approximately 12:45 p.m.

(EDT) on the day of launch.

During the sixth orbit, about 2:30 p.m. (EDT), the satellite

will send AVCS pictures of the Eastern United States to the NASA

North Carolina station for immediate microwave transmission to Goddard.



-7-

: 'U 2 has been put through the most severe test program of

any unmanlmed satellite built to date. Testing included extreme

shaking of a Nimbus prototype from five cycles to 2000; centrifuge

teats with loads up to 15 Gs (15 times the pull of gravity) and

cycling in the thermal vacuum chamber of heat and cold for several

weeks.

Then during the summer of 1962, nuclear testing created an

artificial radiation belt in the area where the satellite would later

orbit. As a result, solar cells on the spacecraft were replaced by

a new type havihg more resistance to radiation damage.



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i VLbJUS BACKGROUND INFORMATION

August 1964 Launch Pacific Missile Range

ContentsTitle Page

TECHNICAL INFORMATION . . . . . ... . . . . . 7

Nimbus Spacecraft . . . . . . ... . . . . . . 9

Attitude Control Sub-System . . . . . . . . . 9

Power Supply . . . . . . . . . . . . . . . . . 11

Advanced Vidicon Camera System . . . . . . . . 12

Automatic Picture Transmission Camera . . . . . 14

High Resolution Infrared Radiometer (HIUR) . . 16



O-9

Nimbus SDacecraft

4 1The

Nimbus spacecraft includes an upper attitude control section

built by General Electric Co., the lower sensory section, and an

interconnecting truss structure. The spacecraft stands 10 feet tall

and weighs 830 pounds.

The truss structure connects the upper hexagonal control section

and the sensory housing or ring at three points. It provides the

critical alignment required between the two sections.

Weather sensing equipment and associated electronics are housed



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attitude-control ecbsystems, and provides unobstructed exposed

mounting for the Sun sensors, horizon scanners, control nozzles,

and the command antenna. Two large solar paddles, 8 feet tall by

2.75 feet wide, attach to control shafts projecting from the control

housing and contain 10,500 solar cells.

Primary requirements of the control subsystem are to orient

and stabilize the spacecraft with respect to the Earth and the

orbit plane, and the solar paddles with respect to the Sun.

Nimbus' control subsystem uses two infrared horizon scanners,



, ~-11.-

: Power Supply

To operate a large spacecraft like Nimbus fo r extended periods

requires a tremendous amount of power as compared to the smaller,

frst-gene-ation satellites.

! During periods of full solar illumination, the initial solar

array power output is 450 watts. The average power output for all

spacecraft requirements is 250 watts.

Major components of the Nimbus power supply, which deliver minus

24.5 volts regulated within plus or minus two per cent, are an array



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To help lower the operating temperatures of the cells, a red-

blue filter rejects that portion of the spectrum in which the cells

are insensitive.

The expected average paddle-operating temperature is approximately

plus 100 degreesFahrenheit with extremes ranging from a minus 176

degrees to plus 140 degrees.

The Nimbus storage batteries are packaged into seven parallil-

connected modules, each consisting of 23 series-connected nickel

cadmium cells. Each cell has a 3.2 ampere-hour capacity with a mini-

mum terminal voltage, at discharge, of 1.15 volts.



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If O -13-

I7V cameras deployed, n a fan-like array to produce a three-segment

composite picture.

Each camera covers a 37-degree field-of-view with th e center

camera pointing straight down (local vertical). The optical axis

of the second and third units are rotated 35 degrees to the right

and left of local vertical. This arrangement produces a composite picture

providing the lateral field-of-view (with two degree overlap) necessary

to cover the 26-degree rotation of the Earth between spacecraft passes.

The three-strip picture from the AVCS picture will show an area of



The TV tubes in the advanced vidicon cameras are 800-scan-

line, 1-inch-diameter vidicons giving a linear resolution of about

one-half mile at the optical center at an altitude of 575 statute

miles.

For storing pictures for playback later, the AVCS has a tape

recorder with 1200 feet of tape to record two complete orbits of

192 pictures. A limit switch stops the recorder when the tape is

filled to capacity.

A full two orbits of pictures can be sent from the spacecraft



to -15-

A timer in the APT subsystem programs the equipment for

continuous cycles of prepare and expose during the first eight

ISecondsf each 208-second picture cycle. The remaining 200 seconds

is used to read out the photographs at ground stations at a scan

rate of four lines per second.

Four major elements make up the APT subsystem in the spacecraft:

the sensory housing which contains the camera; vidicon and vidicon

electronics; a video electronic module consisting of a video detector

and timing and switching circuitry; power converters and an FM

transmitter using the 136.9 megacycle frequency.



-16-

H rrh Rezolution Infrared Radiometer

So meteorologists can receive nighttime weather information,

a High Resolution Infrared Radiometer made by International Telephone

and Telegraph Co., is installed in Nimbus. This operates for approxi-

mately 40 minutes during each orbit.

The highly sensitive HRIR, weighing about 12 pounds, will map

nighttime cloud cover by measuring the energy received in a narrow

spectral range (3.4 - 4.2 microns).

In contrast to television the HRIR forms no image. Cloud-



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From an altitude oL 575 miles the HRIR has an instantaneous

field of view of 8.6 milliradians which corresponds to a linear

resolution of five miles below the vertical.

The radiometer output is fed to a FM modulator and then to a

tape recorder which is similar to the AVCS tape recorder. At the

* same time a 10-kc time signal is placed on the tape from a clock in

the spacecraft. The recorder accepts data at a tape speed of 3.75 inches

j per second.

A multiplexer receives the recorded information and the infrared



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The clock usez a crystal-stabilized oscillator which provides

absolute time determination to relate the orbital location of the

spacecraft to its geographical position. The 800-kc aged crystal is

sealed in glass and maintained at a constant temperature by a heating

coil which provides accurate timing reference.

Nimbus receives command signals from the Data Acquisition

Facilities (DAF) ground stations in North Carolina or Alaska through

a whip antenna mounted on top of the attitude control section.

The command receivers reproduce the code generated by the DAF



0 . -19-

Ieat and cold are controlled in the sensory ring and control

section by pneumatically activated shutters on the outside of the

two sections. These shutters open and close automatically.

Telemetry Subsystem

Nimbus uses a pulse code modulation (PCM) telemetry system,

designed by Radiation, Inc., for transmitting information via a

transmitter through a phased array antenna to the ground stations. The

PCM/A4 transmitter is built by Hughes Aircraft Co.

One mode provides stored data, on a Raymond Engineering tape



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This Centier, operated by General Electric personnel under

contract to NASA, evaluates spacecraft performance and determinesall

of the commands to be sent to the spacecraft from Rosman, N.C. and

Gilmore Creek, Alaska.

Functions of the NTCC are:

. Prepare all spacecraft command sequences.

. Perform6 continuing analysis of key spacecraft parameters.

. Determine corrective action in case of spacecraft subsystemmalfunction.

. Specify the sequence of system data processing.



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"Bonai WJeath'er Satellite Center

:;ill1 nadzc, wsasc.mL-nate, ao.- c:'ch.1ive tIl, cloud data used for

cocIat ocual mcteorological purposes.

The antennas at the Rosman and Gilmore sites are identical.

TIho surface of the large antennas consists of a double-curved

aluminum sheet panels which are separatedfrom

thereflector structure

to permit independent adjustment.

The antennas have a gain of approximately 50 db at 1700 mc, with

a -bea:-xid'tih of 0.6 degrees. At 136 me, the antennas have a gain of



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One z ax t the Gmc. C:reck site and the other is at Goddard.

The Gilmore IDMI organi1zation will be manned by four 12-man teams

around the clock. Each team will consist of the following:

. One data operations supervisor,

. One AVCS/HRIR engineer,

. Two AVCS/HRIR technicians,

. One spacecraft systems engineer,

Ile meteorological analyst,

Two computer programmers,

One commBared console operator,



-a

~ j) Tho Lzequenlc~ for zerndx~n- meteorological data from. Timbuz to

the r-rou~nd isas 2~ollo-ao: Zrnmediately after the satellite has been

acquired, the sat-ellite's S-band transmitter is turned on by command

from the ground.

After 45 seconds of S-band warmup, the spacecraft begins sendingI VCS and HRIR stored weather data.

I1-IHRIR data are recorded on two tape recorders at the ground

i station, processed on-line, and recorded on 70mmn filmstrip.

Approximately 20 minutes is required for photographic processing before

3 the HRIR film data are ready for review.



'1 -24 1

"iimpJlicityand real-time pictures make the Automatic Picture

Transiissilon camera extremely appealing to the local weatherman

A typr..l'. c ground station, manufactured by Fairchild Stratos, Inc.,

consists of. manually tracked 13 db helix antenna (about 12-feet long),

a commercially available radio receiver, and a standard facsimile

machine. The 800-line APT picture and 0.25 scanning time per line

are comparable with standard 240 rpm facsimile equipment.

APT pictures are sent to the ground by a five-watt transmitter,



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APr2 Grou-ond Stations

NASA Stations

NASA/Goddard Space Flight CenterCreenbelt, Md.

Radio Corp. of AmericaPrinceton, N.J.

Fairchild-Stratos Corp.Bay Shore, N.Y.

Wallops Island, Va.

Point Mugu, Calif.

Fairbanks, Alaska



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M-Wnna-ional Participation

IO7, Caloba ObservatoryBombay, India

Centre D'etudes Meteorologigues SpatialeLannion, France

* National Research CouncilOttawa, Ontario, Canada

* Meteorological OfficeBrachnell, Berkshire, England

* Offenbach Am MainFederal Republic of Germany

* Danish Meteorological InstituteCopen1bagen, Denmark

* Department of InteriorMelbourne, Australia



-27-

1'a'lalS .prt Forces AntarcticaC r I;cu-.- cI, New ZealandU.'.-. * 3arato,,a

U. S. Army

U.S. Army Electronics R&D LaboratoryFort Monmouth, N.J.

U.S.A.F. Air Weather Service

L. G. Hanscom FieldBedford, Mass.

Offutt AFBOmaha, Neb.

Ent AFB, Colo.

Langley AFB, Va.



'a'hr quadron, Tan-Son-irhut, Viet Nam

'Joather lng,, Patrick AFB, Fla.

Private Users

* Univer3ity of WisconsinMadison, Wis.

* VLAC-TVNashville, Tenn.

* RCA Victor Co.

Montreal, Canada

* California Computer Products, Inc.Anaheim, Calif.

* Built their own stations.



-29-

. ors Roc-:ctdt-ncd engine will burn for 148 seconds. The

rocket will continue its flight powered by the vernier engines

which position tha vehicle in response to signals from the ground.

* At the desired altitude and velocity, about 157 seconds after

launch, the vernier engines cut off and a 33-second coast period

begins before Agena fires.

l1 The upper-stage Agena-B, which is 20 feet long and five feet in

diameter, made by Lockheed Missiles and Space Co., has a two-burn

i1 capability. The launch time is restricted by the "high-noon"



-30- *0j:

At 190 seconds after launch, Agena fires for the first time,

and five secondslater a programmed signal jettisons the protective

shroud which covers the spacecraft ejecting it out into space. 4

The shroud is 19 feet high and resembles a giant-clam shell.

Approximately 237 seconds after Agena ignites, the engine will

shut down and the entire Agena vehicle and spacecraft will coast from

100 miles high to 575 miles. At this altitude Agena will fire for

three seconds and kick the Nimbus into a circular near-polar, 575

statute miles orbit.



I FZ-)-31-

FOllowIfln APgena second burn shutdowns the vehicle is stabilized

by the Arena control system. The Agena horizon scanners are then

turned off, and an 80-degree pitch-up maneuver is executed at a

rate of one degree per second.

Explosive boltcutters or. the V-band separation clamp securing

the spacecraft to the adapter are ignited 112 seconds after the

second burnout and the spacecraft and Agena are separated.

Calibrated separation springs provide a separation velocity

of four feet per second. The delay in separation eliminates the



Launch ti..e changos w:itnh solar declination and is shown in

the following table:

Date Onens Optimum Closes

August

12-14 4:04 a.m. 4:38 a.m. 5:12 a.m.

15-17 4:03 a.m. 4:37 a.m. 5:11 a.m.

18-19 4:02 a.m. 4:36 a.m. 5:09 a.m.

20-22 4:01 a.m. 4:35 a.m. 5:08 a.m.

23-24 4:00 a.m. 4.33 a.m. 5:07 a.m.



0 D

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propulsion Roclkctdyne main Bell mlain enginenCsine arnd two verniers

guidancc autopilot for first Minneapolis Honeywell90 seconds of flight inertial reference arnd

| then ground controlled Barnes horizon sensor

Bell Telephone Lab.system

diameter 8 feet 5 feet

contractor Douglas Aircraft Co. Tockheed Missile andSanta Monica, Calif. Space Co., Sunnyvale,

Calif.

Total lift off weight with Nimbus spacecraft: 123,681 pounds



-34-

J. I. oimsendc is Assistant Director, Space Sciences and

Satellite Applications. William G. Stroud is Chief, Aeronomy and

Meteorology Division. Nimbus Project Manager is Harry Press.

Joseph 3. Schwartz is Goddard Range Operations and Support Officer,

Point Arguello, Calif.

Vehicle systems management is under NASA's Lewis Research Center,

Cleveland, Dr. Abe Silverstein is Center Director. Dr. S. C. Himmel,

Agena Project Manager and Paul C. Winslow, Jr., Agena Project Engineer.

Launch of Nimbus is, by the U.S. Air Force 6595th Aerospace Test

Wing under technical supervision of GSFC. Col. Roy



TWe :-cr boo.ctr Ad bu-2Ic by the Douglas Aircraft Co., Santa

Mcnica, Calif. and the f"c-na-B upper stage is built by the Lockheed

Iissile and Space Co. Sunnyvale, Calif.

Subsystem Contractors

Company Responsibility

California Computer Products Command clockLos Angeles

Control Data Corp. Components for Nimbus Data

Minneapolis, Minn. Handling System

Fairchild Stratos Inc. Automatic Picture Transmission

Bay Shore, N.Y. Ground Equipment



ROTATION~

SPACECRAFT S

XSECOND ORBIT

- -U I PAYs

s'-CONDI2 O'fDIT



'4- -

/V



APTPICTURE

.. .... . e.<\ .... ROUND STATIONS RDIN

.:COMMA-ND AND.'DATA ACOUISITION ..

COTRLUNTD DINTEGRATION METEOROLOGICALTV AND RADIA1ON DATA R OSERVATIONS

NGNENGODA~RDTDDT

EMERGENCY DAAA SPACEFLIGHT--- ----- JCENTERr

TELEV190ON SPCCAT AND HRIR - w- X>ATCA DHAA DTA DATA NEPHANALYSIS MAP S1ORM IDENTIFICATIONM

rI

ARCHIVAL

SCIENTIFIC AND ECHN - WEATHER

R EC OR D SCENTER

SNOW & ICE MAP |

- Nimbus Program Data Flow

00

0-



ATTITUDE COUSTROL HOUSING

COERMOL SCSH1ER

TELEMETRYNTNN eTEtN aTIAN

SOLAR PADDLE a n y SCAMERA

COARSE SUiWENSORSOLAR PADDLE

SUN SENSORYAW 14OZZLES

PNEUMATIC TANtK

SOLAR PADDLE

INTERCONNECTING TRUSS-

THERMAL CONTROL SHUTTERS

BEACON AND P1,,

TELEMETRY ANTENNAS-DAND ANTENNA

HIGH-RESOLUTION AC AEA

IN~FRARED RECORDERAVSRCDE

HIGH-RESOLUTIOrN INFRARED RADIOWETER

ATATAUTOMAT!S DVCECTIO-J, INORBIT

PICTURE-TRA!4SSAISSIO4 ANTENNA PICTURE*TRAHSMISSION CA -RA

-Nimbus A( ecraft

nimbus a press kit

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