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NATIONAL CENTER FOR A T M O S P H E R I C R ES EARCH

B O U L D E R , C O L O R A D O

No. 14, May, 1964Issued each March, May,

July, September and November.

Second-class postage paid at Boulder, Colorado.

FLY NOW; PLAY (BACK) LATER

N C A R Offers Digital Telemetry and Command

System for Balloon ExperimentsA digital telemetry and command system has been

designed and assembled at NCAR for the use of scientists who have balloon-borne experiments to fly. The equipment has been built so that scientists can concentrate their efforts on their experiments without expending money and effort on the problem of how to get information to and from the balloon.

The system, complete with both balloon-borne and ground-station telemetry and command equipment, will be available on a loan basis. NCAR personnel can be called upon to provide engineering assistance so as to integrate the telemetry equipment with the scientific experiment. The telemetry system will handle 49 channels of data, and the command system can transmit 30 different commands.

SEVERAL UNITS PLANNED

One ground station is presently being installed at the NCAR Scientific Balloon Flight Station at Palestine, Texas. During the next six months, two additional ground stations will be installed in mobile vans to pro­vide flexibility of operation and down-range capabilities for flights of long duration.

Two balloon-borne telemetry and command sys­tems have been constructed and are now undergoing bench tests, with flight testing scheduled for June and July. Additional units will be built as they are needed.

TELEMETRY SYSTEM

The balloon-borne portion of the telemetry sys­tem, shown in the upper left-hand corner of the system block diagram on the next page, consists of a data encoder and a transmitter. The data encoder converts up to 41 channels of analog (voltage) inputs into a digital format for transmission to the ground. Each

2 SC IENTIFIC BALLOONING

input, which accepts voltages ranging be­tween 0 and 100 volts, has its own gain adjustments network. These analog inputs are then digitized by the data encoder.

In addition to the analog inputs, there are six digital input channels, with twelve binary bits per channel. There are also two channels of frequency-modulated telem­etry for use by experimenters who require more frequent data sampling than the 15- second interval of any given channel in the pulse-code-modulated (PCM) telemetry. Output of the data encoder is transmitted to the ground by a phase-modulated one- watt transmitter operating at 406.975 Me/ sec.

On the ground, the signal is demod­ulated by a phase-locked receiver. The sig­nal is then processed by the telemetry de­

coder which puts the data into a form that can be conveniently displayed and record­ed. A pair of strip chart recorders is used to record the two FM channels. The digital data are displayed visually on a lighted panel, and are also printed on paper and punched onto paper tape by a Flexowriter. The punched paper tape can be used to process experimental data automatically.

TAPE RECORDER

Mounted in the ground station is a seven-track tape recorder which is used to record telemetry and command data on magnetic tape. It will be possible essentially to re-fly a balloon flight by playing back the taped flight record. Not all seven tracks

(Continued on page 12; ■specifications, pages 8-11)

SYSTEM BLOCK DIAGRAM

BALLO ON-BORNE COMPONENTS GROUND STATION COMPONENTS

IN P U T S TO FM C H A N N E L *

V

T ELEM ET R Y TELEM ETRY

DATA TRANSM ITTER

E N C O D ER

uTELEM ETRY

TELEM ET R Y

R E C E IV ER

TAPE

RECORDER

C O M M AN D COM M ANDREC E IV ER

A

DECODER

COMMANDTRANSM ITTER

T E L E M E T R Y

DECO D ER

V ISU A L

READ OUT

ST R IP

RECO RDER

FLEX O W R ITER ft TAPE PUNCH

COMMAND

ENCODER

THE FLIGHT RECORD Balloon specifications

Flight (polyethyleneDote

(1963-64) Location Sponsor Investigatoroperation

conducted byunless specified; (vol. in cu. ft.)

Oct. 1 Chico, Calif. AFCRL J. Dwyer (AFCRL)

AFCRL 2 mil 800,000

Oct. 4 Clifton- Morenci, Ariz.

NASA Col. Ely (AFCRL)

AFCRL 1.5 mil 2.69 million

Oct. 5 Chico, Calif. AFCRL J. Dwyer (AFCRL)

AFCRL 2 mil 800,000

Nov. 1 Silver City, N.M.

USAF Col. L. Foster (SSD)

AFCRL 1.5 mil 2.94 million

Nov. 3 Truth or Consequences, N. M.

»» »» »

Nov. 8 Holloman AFB, N.M.

ARPA C. Tolbert (U. of Texas)

AFCRL 1.5 mil 2.94 million

Nov. 10 Silver City, N. M.

USAF Col. L. Foster (SSD)

AFCRL 1 mil5.02 million

Nov. 16 Chico, Calif. AFCRL A. Korn (AFCRL)

AFCRL 1.5 mil 2.94 million

Nov. 16 ” ” >» »)

Nov. 17 Truth orConsequences,N.M.

USAF Col. L. Foster (SSD)

AFCRL 1 mil5.27 million

Dec. 12 Holloman AFB, N.M.

NASA G. Steffan (Hughes Aircraft)

AFCRL 2 mil 131,400

Dec. 17 White Sands Missile Range, N.M.

AFCRL B. Gildenberg (AFCRL)

AFCRL 2x1.5 mil 250,000

Feb. 7 Point Barrow, Alaska

NSF J. Winckler (U. of Minn.)

Raven .5 mil 100,000

Feb. 12 Chico, Calif. AFCRL R. Cowie(AFCRL)

AFCRL 2 mil803,000

Float Flight Payload altitude duration weight

(feet) (hours) (pounds) Experiment Flight notes

80,800 29 1,200 Evaluation of one­way valving duct

107,500 22 717 Cosmic ray studies

81,000 79 1,200 Evaluation of one­way valving duct

107,000 5 858 Re-entry system test

»> 3 777 ”

104,700 5 873 Calibration of oxygen radiation profile of earth

113,000 4 945 Re-entry test

98.000 30 1.200 Quality evaluation

92,000 25 1,600 Quality evaluation (increased payload)

118.500 4 886 Re-entry system test

1,400 3 541 Surveyor Balloon tethered vehicle tests

2 261 Dynamic test of Ascent only; float balloon ascent at altitude not

planned

111.000 21 Polar Circling Balloon Observatory (“POCIBO”)

79,000 25 1,113 Balloon evaluation test

w

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THE FLIGHT RECORD (Continued)

Feb. 17, Point Barrow, NSF J. Winckler Raven1964 Alaska (U. of Minn.)

Feb. 18

Feb. 21 Chico, Calif. AFCRL H. Prevett(AFCRL)

Feb. 26 Holloman AFB, N.M.

AFCRL

AFCRL Capt. G. Schofield AFCRL

Mar. 3 Point Barrow NSF J. WincklerAlaska CU. of Minn.)

Mar. 4 Chico, Calif. DASA, F. Doherty AFCRL (AFCRL)'

Mar. 4 Sioux Falls, ONR S. D.

Raven

AFCRL

Rave

.5 mil 100,000

2 mil803.000

2 mil800.000

1.0 mil 1.5 million

2 mil472.000

.5 mil3 million

Mar. 4 Point Barrow, NSF Alaska

J. Winckler (U. of Minn.)

Raven .5 mil 100.000

Mar. 6 1.0 mil1.5 million

Mar. 10 Chico, Calif.

Mar. 12 Holloman AFB, N.M.

DASA. F. Doherty AFCRL 2 mil AFCRL C AFCRL) 472,000

AFCRL C. Leavitt AFCRL 1.5 mil(U. of N.M.) 2.94 million

Mar. 13 Chico, Calif. DASA. F. Doherty AFCRL (AFCRL)

AFCRL 2 mil 472,000

Mar. 13 Point Barrow, Alaska

J. Winckler < U. of Minn.)

Raven 1.0 mil 1.5 million

20 “POCIBO”

79.000 97 1,114 Test of new flightinstrumentation

92.000 6 450 Balloondynamics test

109,000 ...... 510 “POCIBO”

64,000 5 1,800 Balloon evaluation& “C” launch test

125,000 4 600 Combined test ofnew balloon-borne camera and simu­lated variable thick­ness (SVT) balloon design

20

53,000 7 535

63.200 6 1,800 Balloon evaluationand “C” launch test

113,000 6 561 Measurement ofenergetic neutrons

64.300 3 1,800 Balloon evaluationand “C” launch test

Balloon burst

Balloon burst at altitude

Balloon leaked

604 Balloon burst shortly after release

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Mar. 16, Chico, Calif. 1964

Mar. 17 Palestine, Tex.

DASA, F. DohertyAFCRL (AFCRL)

ONR, D. GatesNBS (NBS)

Mar 26 Holloman AFB, N.M.

AFCRL D. Murcray(U. of Denver)

Mar. 27 Holloman AFB, N.M.

Mar. 31 Palestine, Tex.

AFCRL J. Salisbury (AFCRL)A. Howell (Tufts U.)

ONR, D. Gates NBS (NBS)

Apr. 9 Page, Ariz. NSF Z. SekeraC. Rao (UCLA)

Apr. 17 Page, Ariz. NASA A. Shipley(NCAR)

Apr. 17 Chico, Calif. AFCRL R. Toolin(AFCRL)

Apr. 21 Chico, Calif. AFCRL J. Dwver(AFCRL)

AFCRL

NCAR

AFCRL

AFCRL

NCAR

NCAR

NCAR

AFCRL

AFCRL

May 12 Palestine, NASA K. McCracken NCARTex. (Grad. Res. Ctr.

of S.W.)

2 mil 63,300 5 1,766 Balloon evaluation472.000 and “C” launch test

.75 mil __ ...__ ___ 1,505 Atmospheric Electrostatic10 million moisture charge caused

measurements squib to fire seconds after launch

1.0 mil 105,000 4 1,000 Water vapor2.07 million measurements in the

2.7-angstrom region

1 mil & 1 mil cap 106,000 27 1,647 Infrared observations5.025 million of the moon

.75 mil 10 million

119,800 1,464 Atmosphericmoisturemeasurements

Balloon valved down to 88,000 ft. for termination

1.5 mil 250,000

79,000 457 Skylightpolarimeter

.32 mil (avg.) 1.25 million

25

1.5 mil 2.94- million

2 mil 800.000

106.000

83.000

Test flight of extreme altitude balloon

9 700 Albedomeasurements

32 1,200 Test of one-way valving duct

Balloon was composite of thin polyethylene bonded with strength members. Balloon burst at72.000 ft.; theoretical design altitude: 150,000 ft.

.75 m il3 m illion

125,000 26 450 Cosmic ray detector

UPCOMING FLIGHTS

Dote(1964) Location Sponsor

May Page, Ariz. NASA

May Sioux Falls, NASA S.D.

May Northfield, ONR Minn.

June Palestine, U.S.Tex. Army

June Palestine, AECTex.

June Palestine, AEC Tex.

June Palestine, NASATex.

June Palestine, NASA Tex.

June Palestine, NSFTex. ONR

NASA

July Palestine, NASATex.

Aug. Bruning, GSFCNebr.

Balloon specifications (polyethylene Float

unless specified; altitudeInvestigator

A. Shipley (NCAR)

R. Doolittle (Thompson Ramo

Wooldridge)

E. Pybus (BRL, Aberdeen Proving Ground)

H. Mark(Livermore Labs.)

G. Frye (Case Inst.)

M. Kaplon (U. of Rochester)

A. Barrett (MIT)

M. Schwarzschild (Princeton U.)

T. Parnell (U. of N.C.)

D. Kniffen

vol. in cu. ft.) (feet)

.32 mil 150,0001.25 million

.75 mil 104,000800,000

.5 mil Mylar 150,000scrim10 million

.75 mil 100,000450,000

.75 mil 120,0006 million

.5 mil 128,0003 million

.75 mil 132,0008.5 million

1 mil 100,0001.25 million

Launch balloon 80,000 0.5 mil, 300,000; main balloon;0.35 mil,5.25 million;Dacron &Mylar scrim

.75 mil 125,0003 million

.75 mil 130.0003 million

Fliqhtduration(hours)

3

12

4-6

4

8

24

8

12

36

10

Payloadweight

(pounds) Experiment Remarks

25 Test flight of extreme Balloon to be com- altitude balloon posite of thin poly-

ethlyene bonded with strength members

200 Luminescent chamber for collecting cosmic ray data

Tandem balloon development

145 Water vapor 2 flights—ascent tomeasurements 100,000 ft. and

40

terminate

170 Gamma ray 2 flightsastronomy

195 Gamma ray and 2 flights charge particle detector

100 Oxygen spectrum 2 flights experiments

11,000 Test flight ofimproved balloon and flight components

80 Cosmic ray studies 3 flights; total time at altitude, 36 hours

140 Oriented emulsions

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UPCOMING FLIGHTS (Continued)

Summer Skyhook Series*:

June Fort Chunthrough Manitoba,Aug. Canada (1964)

Aug. Flin Flon, Manitoba, Canada

NASAGSFC

D. Guss (GSFC)

.75 mil 9 million

140,000 10-15

” ” .75 mil 600,000

102,000 »»

ONR W. Webber (U. of Minn.)

.75 mil 1.5 million

120,000 12

ONR C. Waddington (U. of Minn.)

.75 mil 9 million

140,000 10

” » >»

ONR J. Earl(U. of Minn.)

.75 mil 3 million

130,000 12

NASA P. Meyer (U. of Chicago)

.75 mil 3 million

125,000 12

” .75 mil 9 million

130,000 20

” ” ” 135,000 ”

NRL B. Stiller (NRL)

.75 mil 9 million

140,000 12

NASA K. McCracken (Grad. Res. Ctr. of S.W.)

.75 mil 3 million

125,000 24

” »» .75 mil 9 million

135,000 16

AEC G. Frye (Case Inst.)

.5 mil 3 million

120,000 12

NSF J. Winckler (U. of Minn.)

.75 mil -------100,000-300,000

20-40

ONR K. Anderson (U. of Calif., Berkeley)

.5 mil 1 million

120,000 10

NASA ” .5 mil 1.5 million

135,000 »

*For piggyback information on the summer Skyhook series interested parties should contact:

130 Emulsions and counters

2 flights

»» >>

50 Counter

120 Emulsions

60100 Counters 2 flights

120 Counters 4 flights

500 Spark chamber 3 flights

15080

CountersEmulsions

2 flights

100 ----- 3 flights

75 ----- 2 flights

175 Spark chamber 2 flights

12 Solar flare studies 10 flights

60 Counters 5 flights

" 3 flights

Cmdr. Walter Martin, ONR Field Representative for Balloon Operations, Physics Department, University of Minnesota, Minneapolis, Minnesota

vi

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Telemetry and Command System

Telemetry

Component and Function T e l e m e t r y D a t a E n c o d e r

To convert analog and digital infor­mation from a balloon-borne experi­ment into a signal format that can be effectively transmitted to the ground station

T e l e m e t r y T r a n s m it t e r

To transmit the encoded data to the ground station

Technical CharacteristicsNumber of inputs: 41 analog and 6 digital Input voltage range: 0-100 volts Gain: Each channel is independently adjust­

ableEncoding accuracy: ± .3% of full scale except

for signal levels under .5 V Time: Automatically encoded as one of the

digital words. Measured in tenths of hours from time of reset

Digital format: Non-return to zero; pulse code modulated; 16 bits per word, 32 words per frame; 16 words are subcommutated

Information rate: 34.133 bits/sec (four frames /min)

Frequency modulation channels: Two sub­carriers, 2300 cps and 7350 cps

Weight: 17 lbs Size ( inches): 12/2 x 13M x 4 Power: 26-32 V, 250 mA

Transmitted power: 1 W Modulation: PhaseFrequency: 406.975 Mc/sec crystal controlledWeight: 2 lbsSize (inches); 1 0 x 4 x 3Power in: 12 V at 50 mA and 24 V at 70 mA

Command

Component and Function

C o m m a n d R e c e i v e r

To receive command signals trans­mitted from the ground station

Technical Characteristics

Receiver type: Double conversion FM Frequency: 149.4 Mc/sec crystal controlled Private line: Receiver rejects all signals that do

not contain the private line tone Weight: 2 lbs Size ( inches): 13 x 3M x 2 Power: Supplied by command decoder

SCIENTIFIC BALLOONING 9

Specifications : Balloon-Borne Components

C o m m a n d D e c o d e r

To identify and actuate commands

I

Number of commands: 30 Momentary contact relays: Activated by com­

mands 1 through 10 Latching relays: Activated by commands 11

through 20. Released by commands 21 through 30

Relay contacts: Double pole, double throw.Rated at 2A

External connections: All contact and coil con­nections from the relays are wired to an external connector

Security features: Digitally coded signals in the form of 800-cps tone bursts are re­quired to activate the decoder. Each com­mand must be received twice: once in a normal form and then in an inverted form

Weight: 10 lbs. Size (inches): 12/4x7x4 Poioer: 26 to 32 V at 150 mA

SCIENTIFIC BALLOONING SCIENTIFIC BALLOONING

Telemetry and Command System Specifications : Ground Station Components

Telemetry

Component and Function

T e l e m e t r y R e c e i v e r

To receive the telemetry signal from the balloon-borne telemetry trans­mitter

T FT.KivfF.TRY D e c o d in g E q u i p m e n t

To convert the telemetry signal into a form that can be displayed and/or recorded

S t r i p C h a r t R e c o r d e r s

To record and display the information on the two FM telemetry channels

V i s u a l R e a d o u t

To display visually the digitally en­coded data

F l e x o w r i t e r

To make a record of the telemetry information on paper and on punched paper tape and to provide a visual display

Technical Characteristics

Receiver type: Double superheterodyne with phase-locked FM discriminator

Frequency: Tunable from 370 Mc/sec to 410 Mc/sec

Subcarrier discriminators demodulate the 1300- cps PCM, and 2300- and 7350-cps FM subcarrier signals

Bit synchronizer provides synchronization for 34.133-bit-per-sec PCM signal

PCM (pulse code modulation) decommutator provides frame and sub-frame synchroni­zation of digital data. Arranges PCM data in form compatible with Flexowriter, vis­ual readout and command encoder

Number of recorders: Two Chart size-. Five-in. writing width, 100 ft. long Chart speeds: 1, 2, 4, or 8 divisions per hour

and 1, 2, 4, or 8 divisions per minute (1 division = 0.1 in.)

Response: Full scale, .5 sec Accuracy: .2% of full scale

Number of readouts: Two Method of display: 3 illuminated Arabic digits Number of displayed channels: All 47 digitally

coded channels Channel selection by thumb wheel switch

Data format: Flexowriter starts at left margin; types first channel of data as 3-digit num­ber; spaces; types second channel. Repeats process to 30th channel, returns carriage and starts over

Subcommutated data contained on channel 16 Type rate: 8.5 characters/see or 2.1 channels/

secTape punch: All typed data can be recorded

simultaneously on 8-channel punched tape

T a p e R e c o r d e r

To make a magnetic tape record of both command and telemetry informa­tion

Number of tracks: Seven Method of recording: Direct or FM Recording tape: M-in., on 10-in. reel Tape speed: lJs, 3/2, 7'2, and 15 in./sec Max. recording time: 8 hrs 32 mins using .5

mil tape, 6 hrs 24 mins using 1 mil tape, and 4 hrs 16 mins using 1.5 mil tape

1

Command

Component and Function

C o m m a n d E n c o d e r

To encode digital commands transmission to the balloon

Technical Characteristics

for

C o m m a n d T r a n s m it t e r

To transmit command signals to the balloon

Number of commands: 30 Method of selecting command: 31 push but­

tons (two simultaneously for cut-down) Method of activating command: Separate “ac­

tivate” push button Encoded format: Digitally coded in the form

of pulse-width-modulated, 800-eps tone bursts. Each command transmitted twice: once normal and once inverted

Command verification: The “command select” push button is illuminated when the tele­metry system verifies that the command has been received

Frequency: 149.4 Mc/sec, crystal controlled Private line used when commanding balloon Communications: A receiver is also mounted

in the ground station. The receiver-trans- mitter combination can thus be used to provide voice communication between control stations

12 SCIENTIFIC BALLOONING

are required for telemetry and command recording; on the average, the experimenter can count on five tracks being available to him.

COM M AND SYSTEM

Commands are sent to the balloon by pushing one of thirty “command select” buttons on a panel in the ground station console. The selected command is then transmitted by pushing the “command acti­vate” button. The use of two separate oper­ations per command makes the chance of sending a command by mistake unlikely. An additional degree of security is pro­vided for the cut-down command: two se­lection buttons labeled “cut-down” must be pushed at the same time.

Commands are digitally encoded in the form of a train of 800-cps tone pulses. The digitally-coded signal is then transmitted to the balloon by a transmitter operating at 149.4 Mc/sec.

In the balloon, the command decoder activates commands by closing relay con­tacts. When a command is received, a veri­fication signal is transmitted through the telemetry system to the ground station. The verification signal turns on a light inside the command push button, thus notifying

the operator that the command has been received,

FUTURE ADDITIONS

A balloon-borne tape recorder and a ranging system are planned for the future. The tape recorder will record the telemetry signal before it is transmitted to the ground station. Use of the tape recorder will make possible the recovery of the experimental data even if the telemetry link should mal­function during a flight.

The ranging system, to measure the slant-range distance from ground station to balloon, is presently under development. When the system is put into use, the ap­proximate position of the balloon can be obtained at any time by measuring the range and the direction from which a maximum signal is received. When the two additional, planned ground stations are in operation, it will be possible to obtain very accurate positional fixes by locating the intersection point of the loci of two range measurements.FOR FURTHER INFORMATION

Experimenters who are interested in using the telemetry and command equip­ment should contact either Vincent E. Lally or Ernest W. Lichfield at the National Center for Atmospheric Research, 1420 30th Street, Boulder, Colorado 80301.

PUBLISHED BY THENATIO NAL CENTER FOR ATMOSPHERIC RESEARCHOPERATED BY THE UNIVERSITY CORPORATION FOR ATMOSPHERIC RESEARCH AND SPONSORED BY THE NATIONAL SCIENCE FOUNDATION ADDRESS REQUESTS FOR COPIES TO NCAR, BOULDER, COLORADO 80301