APPENDIX F

DC-8 DATA DISTRIBUTION SYSTEM (DADS) CHARACTERISTICS

 

 

 

DC-8 Data Acquisition and Distribution System (DADS)

Characteristics and Output Products

DC-8 DADS Data Products

A. In-Flight Data Products

During each flight there are several DADS displays, viewable on monitors throughout the cabin. The DADS Parameter Display (see table F1) shows a subset of DADS data in table format. The Track Plot Display shows the aircraft flight track superimposed on a reference map. The Real-Time Plot shows several parameters as a color graph, generally in a time-series strip chart format. All of these are configurable as required and are continuously updated. In addition, the Weather Satellite APT Receiver displays real-time satellite images from the NOAA polar orbiters whenever available. It is also be possible to graphically examine all DADS parameters from any portion of the flight at the DADS station computer if necessary.

The DC-8 DADS serial transfer of housekeeping data is available in-flight to allow easy access to aircraft data by experimenter computers. The data is in ASCII format, in engineering units Data is sent at one second intervals with transmission rates of 1200, 9600, and 19.2K baud. Format and hardware interface requirements are described in another section below.

B. Post-Flight Data Products

After each flight several hardcopy DADS data products will be available. The DC-8 Mission Director Log will contain time/data stamped commentary on the flight. A set of Track Plots will show the DC-8 flight track, including flight-level winds. A set of Time-Series Plots will show a selection of DADS parameters. The Parameter Printout will contain 10-second picks of representative parameters. Other graphical products may be produced by request of the Mission Director. All of these products will be given to the GTE Project Office after each flight, in both hardcopy and electronic format. The DADS ASCII-formatted data set will also be submitted.

 

 

TABLE F1. DADS Parameter Display (PEM Tropics Preliminary)
Parmeter Format Units Parmeter Format Units

DAY

ddd

 

TIME

hh:mm:ss

 
           

LATITUDE

+dd mm.m

 

PITCH

xxx.x

DEG

LONGITUDE

+dd mm.m

 

ROLL

xxxx.x

DEG

           

TRUE HEADING

xxx.x

DEG

PRESSURE ALT

xxxxx

FT

ALGN/FROM/TO

aaaaaaaaaa

 

RADAR ALT

xxxxx

FT

TIME TO GO

xxxx.x

MIN

PRESSURE ALT

xxxxx

M

           

STAT AIR TEMP

xxx.x

C

CABIN ALT

xxxxx

FT

SAT COMPUTED

xxx.x

C

     
     

TRUE AIR SPD

xxx

KTS

D/F POINT 2

xxxxx.x

C

GROUND SPD

xxxx

KTS

D/F POINT 3

xxxxx.x

C

MACH #

x.xxx

 
           

SPECIFIC HUM

x.xxx

G/KG

VERTICAL SPD

xxxxxx

F/MN

           

TOT AIR TEMP

xxx.x

C

WIND SPEED

xxx

FTS

IR SURF TEMP

xxx.x

C

WIND DIR

xxx

DEG

     

DRIFT ANGLE

xxx.x

DEG

POTEN TEMP

xxx.x

K

     
     

SUN EL-RF/AC

xxx.x

DEG

PRESSURE

xxxx.x

MB

SUN AZ-AC

xxx.x

DEG

 

DADS Serial Outputs to Experiments

The DADS ASCII-formatted data is available in real time in-flight through a serial interface, and post-flight as a computer file (9600/19.2K baud format only). This section describes the formats and hardware interface requirements used to access this data.

A. 1200 Baud Data Format

Data is transferred once per second at 1200 baud in two 56-character blocks which each begin with a unique character identifier and end with an ASCII carriage return and line feed. The total number of characters every second is 112. Parameter fields within each block are not separated by a space, but there may be one or more blanks at the end of a block (before the carriage return and line feed) to pad the length to 56 characters. Table F2 shows the configuration, and Table F3 shows an example.

TABLE F2. DADS Serial Output 1200 Baud Block Configuration

Identifier

Parameters

Field Format

Units

A Day aaa day of year
. Time (UT) bb:bb:bb.bbb hour:min:sec
. Latitude ±cc cc.c degrees/minutes
. Longitude ±ddd dd.d degrees/minutes
. Pitch eee.e deg
. Roll ffff.f deg
. Wind speed ggg knots
. Wind direction hhh deg
. True air speed iii knots
. . . .
B Ground speed jjjj knots
. True heading kkk.k deg
. Drift angle lll.l deg
. Pressure altitude mmmmm feet
. Radar altitude nnnnn feet
. Dew/frost point temp
(GE 1011 hygrometer) with state flagged
ooooo.o deg C
. Dew/frost point temp
(EG&G 300 hygrometer) with state flagged
ppppp.p deg C
. Static air temperature qqq.q deg C
. Total air temperature rrr.r deg C
. IR surface temperature sss.s deg C



TABLE F3. DADS Serial Output 1200 Baud Block Example
Aaaabb:bb:bb.bbb±cc cc.c±ddd dd.deee.effff.fggghhhiii <cr><lf>
Bjjjjkkk.klll.lmmmmmnnnnnooooo.oppppp.pqqq.qrrr.rsss.s<cr><lf>
A32101:22:45.105+34 25.0-122 03.0-10.3 -45.6110270450 <cr><lf>
B 425212.3 5.12800024050-1012.4-3012.7-10.1 14.6-15.9<cr><lf>

Key
<cr>
<lf>
ASCII carriage return
ASCII line feed



B. 9600/19.2K Baud Data Format

Data is transferred once per second at 9600 and 19.2K baud in seven 56-character blocks which each begin with a unique character identifier and end with an ASCII carriage return and line feed. The total number of characters available every second is 392. Parameter fields within each block (including the start-of-block character) are separated by at least one space, and there may be one or more blanks at the end of a block (before the carriage return and line feed) to pad the length to 56 characters. The contents of the first five blocks (identifiers C through G) are fixed. The contents of the last two blocks (identifiers H and I) are at the discretion of the Mission Manager and will be configured for PEM Tropics. Table F4 shows the configuration, and Table F5 shows an example.


TABLE F4. DADS Serial Output 9600/19.2K Baud Block Configuration

Identifier

Parameters

Field Format

Units

C Day aaa day of year
. Time (UT) bb:bb:bb.bbb hour:min:sec
. Latitude ±cc cc.c degrees/minutes
. Longitude ±ddd dd.d degrees/minutes
. Pitch eee.e deg
. Roll ffff.f deg
. Wind speed ggg knots
. . . .
D Wind direction hhh deg
. True air speed iii knots
. Ground speed jjjj knots
. True heading kkk.k deg
. Drift angle lll.l deg
. Pressure altitude mmmmm feet
. Radar altitude nnnnn feet
. Dew/forst point temp
(GE 1011 hygrometer) with state flagged
ooooo.o deg C
. Dew/frost point temp
(EG&G 300 hygrometer) with state flagged
ppppp.p deg C
. Static air teemperature qqq.q deg C
. Total air temperature rrr.r deg C
. . .
E IR surface temperature sss.s deg C
. Static air temperature, calculated ttt.t deg C
. Indicated air speed uuu knots
. Vertical speed vvvvv ft/min
. Distance to go wwwww.w nm
. Time to go xxxx.x min
. Align status yy .
. . . .
F Cabin altitude zzzzz feet
. Pressure JJJJ.J mb
. Mach number K.KKK .
. Cross track distance LLLLL.L nm
. Desired track MMMM.M deg
. Track angle error NNNN.N deg
. Track angle OOO.O deg
. Specific humidity P.PPP g H2/kg air
. . . .
G Partial pressure H2O QQ.Q mb
. Relative humidity with respect to ice RR.R %
. Relative humidity with respect to water SS.S %
. Saturation vapor pressure of water TT.TT mb
. Saturation vapor pressure relative to ice UU.UU mb
. Sun elevation in ground reference frame, refracted VVV.V deg
. Sun elevation in aircraft reference frame, refracted WWW.W deg
. Sun azimuth in ground reference frame XXX.X deg
. Sun azimuth in aircraft reference frame relative to the aircraft nose YYYY.Y deg
. . . .
H Contents of this block will be specified by DC-8 Mission Manager
I Contents of this block will be specified by the DC-8 Mission Manager

 

 

TABLE F5. DADS Serial Data 9600/19.2K Baud Block Example

9600/19.2K Baud Block Example

C aaa bb:bb:bb.bbb ±cc cc.c ±ddd dd.d eee.e ffff.f ggg<cr><lf>
D hhh iii jjjj kkk.k lll.l mmmmm nnnnn ooooo.o ppppp.p<cr><lf>
E qqq.q rrr.r sss.s ttt.t uuu vvvvvv wwwww.w xxxx.x yy<cr><lf>
F zzzzz JJJJ.J K.KKK LLLLL.L MMMM.M NNNN.N OOO.O P.PPP<cr><lf>
G QQ.Q RR.R SS.S TT.TT UU.UU VVV.V WWW.W XXX.X YYYY.Y <cr><lf>
H ****************************************************<cr><lf>
I ****************************************************<cr><lf>

C 321 01:22:45.105 +34 25.0 -122 03.0 -10.3 -45.6 110<cr><lf>
D 270 450 425 212.3 5.1 28000 24050 -1012.4 -3012.7<cr><lf>
E -10.1 14.6 -15.9 -9.4 410 -1250 -332.6 50.8 45<cr><lf>
F 5100 466.7 0.714 332.0 240.7 -11.8 202.0 0.269<cr><lf>
G 13.4 15.2 20.2 34.22 37.66 10.6 13.7 252.3 -160.2 <cr><lf>
H ****************************************************<cr><lf>
I ****************************************************<cr><lf>

Key
<cr>
<lf>
****...
ASCII carriage return
ASCII line feed
block content subject to Mission Manager's discretion

 

C. General DADS Serial Output Format Information

All data parameters are in engineering units. For integer formats, the number of digits in a field may vary from one to the number shown above. For other formats, the placement of the decimal point and number of digits to the right of it are guaranteed to be as shown. However, the number of digits to the left of the decimal point may vary from one to the number shown in the field format. Unused leading digits are padded with blanks or zeroes.

Individual parameter fields will be filled with special characters for the following reasons:

Condition

Special Character

Data was too big for parameter field
Data was too small for parameter field
Data formatting error occurred
>
<
?

Additionally, invalid or unavailable data may be replaced by question marks (?), however, the absence of question marks in a parameter field does not guarantee the validity of the data.

D. Hardware Interface Information

The DADS data distribution subsystem provides a well-defined data transfer mechanism between the DADS and onboard experiments. It broadcasts aircraft houskeeping data in ASCII-formatted engineering units via RS-232-C serial connections to experiment stations at one second intervals. Experimenters who want to receive DADS serial data in-flight will have a DADS data box on or near their experimenter station. Each box outputs the data via three RS-232-C female DB-25 connectors, corresponding to the three baud rates, which may be used in any combination. Each DB-25 connector may be configured as a modem (DCE) or a computer (DTE) with a switch, which exchanges pins 2 and 3. There is no handshaking capability between the DADS and the experiments. The outputs are opto-isolated, and the RS-232-C drivers are current limited. The serial protocol is one start bit, 8 data bits, no parity, and one stop bit. Table F6 shows the pinout of the DADS box DB-25 connectors.

TABLE F6. DADS Distribution Box RS-232-C DB-25 Connector Pinout

Pin

 

RS-232

Function

Connection

1
2

3

4
5
6
7
8
20


TD

RD

RTS
CTS
DSR

DCD
DTR
AA
BA

BB

CA
CB
CC
AB
CF
CD
Protective Ground
Transmit Data

Receive Data

Request to Send
Clear to Send
Data Set Ready
Signal Ground
Carrier Detect
Data Terminal Ready


DADS serial data on this pin
(if switch selects pin 2)
DADS serial data on this pin
(if switch selects pin 3)
Jumpered to pin 5
Jumpered to pin 4
Jumpered to pins 8 and 20
DADS signal ground
Jumpered to pins 6 and 20
Jumpered to pins 6 and 8

 

Table F7. DC-8 Ancillary Data

Data Available on Video Monitors Throughout DC-8 Aircraft

Forward Cloud Video
MTP
DIAL Aerosol & Ozone
LASE Aerosol & H2O
Track Plot
Quad of Storm Scope, Polar Satellite Images, Weather Radar & Nadir Cloud Video
DADS and PI Parameter Tabular Displays
DADS and PI Parameter Graphics Displays

Project Supplied Ancillary Data Displayed by DADS

H2O Cryo
NO
CO
CN
O3
Project Supplied Ancillary Data Distributed on SDS
H2O Cryo

 

Responsible NASA Official: Dr. Vic Delnore
Curator: Kay Costulis and Clyde Brown


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Last updated: April 03, 2002