CAMEX-4 DC-8 Information Collection and Transmission System

1. Introduction
2. Content and structure of the ICATS files
  2.1 Description of data files
    2.1.a Files of the type .asa
    2.1.b Files of the type .asc and _rt.asc
    2.1.c Files of the type _md_log
    2.1.d Binary files
  2.2 Graphic representation of flight data
3. Contact Information

1. Introduction

This README file contains information about the DC-8 Information Collection and Transmission System (ICATS) files for flights in support of CAMEX-4. These data files were generated on board the DC-8, saved to disk, and downloaded post flight, and include measurement of aircraft parameters such as airspeed, altitude, roll/pitch/yaw angles, groundspeed, flight level windspeed, temperature and many others.

A complete breakdown of each measured parameter may be found in the following three documents: ICATS-HANDBOOK.pdf, ICATS_format_AppendixB.pdf, and ICATS_appendix_2.pdf. These documents may obtained via ftp from: ftp://microwave.nsstc.nasa.gov/pub/doc/camex4/c4dicats/.

2. Content and structure of the ICATS files

The DC-8 ICATS serial transfer of housekeeping data allows easy access to aircraft data by experimenter-operated computers. The data were transferred at one second intervals. Image files of in flight parameters are generated and saved as post-script files, as are flight track maps (2) one showing flight track and the other showing wind barbs along the flight track, and plotted every 10 minutes.

In all there are 11 files per flight-- eight data files and three post script files. These files are then 'tarred' into a daily /mission file with the following name:

c4d8icats_2001.ddd_0104ff.tar

where:

c4d8icats = CAMEX-4 DC-8 ICATS data

2001.ddd = year 2001, ddd = day of year

0104ff = official DC-8 mission number (e.g. 010413)

tar = 'tarred' file

Once 'untarred', the eleven files will be extracted. Each file has a name of the form: 0104ff[ext] where ff is as above giving the mission number. File extensions [ext] are shown below along with their type (ascii, bin, ps):

.asa - ascii

.asc - ascii

.avg - bin

.nav - bin

.one - bin

.ten - bin

_md_log - ascii

_rt.asc - ascii

map1.ps - ps

map2.ps - ps

plots.ps - ps

Note: files of type "_rt.asc" are subsetted back up files for the ".asc" files, which record data from power on until power off. The _rt.asc files delete a lot of the pre-takeoff data, and actually begin collecting data shortly before the first aircraft movement.

2.1 Description of data files

Data from the ICATS system are tabulated in two tabular ascii files described in 2.1.a and 2.1.b below. Mission manager information, again in ascii, follows in 2.1.c, and binary forms of the data are described in 2.1.d.

2.1.a Files of the type .asa

Typical aircraft data is presented in ascii files with the ".asa" extension. There are two lines of data whose format is found in the decode table. These two lines repeat for the entire flight, and yield data every one second.

A23715:12:00.000+30 13.8-081 40.3 - 1.0   0.5   0   0   0

B   0142.1  0.0   -91     0 2000.0 3000.0  32.0  32.0   33.6

Aaaabb:bb:bb.bbb+cc cc.c-ddd dd.d -ee.e fff.f ggg hhh iii

Bjjjjkkk.k ll.l mmmmm nnnnn oooo.o pppp.p qqq.q rrr.r ssss.s(...)

The second A/B group above is used with the table below for decoding the lines A and B for the .asa files.

 

2.1.b Files of the type .asc and _rt.asc:

More detailed aircraft information is contained in these files. The format shows seven lines, which are repeated every one second of the flight.

C aaa bb:bb:bb.bb +cc cc.c +ddd dd.d eee.e ffff.f ggg
D hhh iii jjjj kkk.k lll.l mmmmm nnnnn ooooo.o ppppp.p
E qqq.q rrr.r sss.s ttt.t uuu vvvvvv wwwww.w xxxx.x yy
F zzzzz JJJJ.J K.KKK LLLLL.L MMMM.M NNNN.N 000.0 P.PPP
G QQ.Q RR.R SS.S TT.TT UU.UU VVV.V WWW.W XXX.X YYYY.Y
Haaa.a bbb.b ccccc ddddd eeeee fffff ggggg hhhhh
Iiii.i jjj.j kkkk.k lllll mmmm.m nnn.n ooo.o ppp.p

These files may be decoded using the following table: 

G

WWW.W

H

egi True Heading

aaa.a

0-360 degrees

bbb.b

0-360 degrees

egi x velocity

ccccc

+/- 9000

egi y velocity

ddddd

+/- 9000

egi z velocity

eeeee

+/- 9000

egi x acceleration

fffff

+/- 1100

egi y acceleration

ggggg

+/- 1100

egi z acceleration

hhhhh

+/- 1100

Air Data Computer Total Air Temp

iii.i

-99.0 to 50.0

Rosemont Total Air Temp

jjj.j

-99.0 to 50.0

Potential Temperature

kkk.k

-999.0 to 1000.0

GPS Altitude MSL

lllll

-2000 - 70000

mmmm.m

-100.0 to 70.0

Sun Elevation Angle wrt Earth

nnn.n

-90.0 to 90.0

Sun Elevation Angle wrt Aircraft

ooo.o

-90.0 to 90.0

Sun Azimuth Angle wrt Earth

ppp.p

0 - 360

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 in the field format. For non-integer formats, the placement of the decimal point within the field and the number of digits to the right of the decimal point are guaranteed as illustrated in the field format. 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 either blanks or zeroes. Units are not included in the data stream.

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

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.

2.1.c Files of the type _md_log:

These are plain text messages which record important events during the flight.

2.1.d Binary files (i.e. files with the given extensions) are described below.

.avg: Averaged, mid-second and raw data. This is the complete binary data containing information from 305 parameters.

.nav: Flight management record data. Includes all important navigation parameters (34 total).

.one: One Hz. binary data of 155 parameters including navigation, wind, waypoint, and aircraft state.

.ten: Ten Hz data of 40 navigation and waypoint data

2.2 Graphic representation of flight data.

In addition to the text version of flight data, postscript (file extension .ps) images of many parameters have been included to display changes during the course of the flight. Also included in the dataset are two flight track maps- one shows position time hacks every ten minutes, and the other includes wind barbs at those positions.

From these postscript files we have created ".GIF" images representing each of the two maps and each of the three graphic panels of the plot of flight parameters.

3. Contact Information

Data can be ordered and questions addressed at http://ghrc.nsstc.nasa.gov/.

To order this data or for further information, please contact: Global Hydrology Resource Center User Services 320 Sparkman Drive Huntsville, AL 35805 Phone: 256-961-7932 E-mail: ghrc@eos.nasa.gov

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NASA Information Contact: Michael Goodman, Global Hydrology and Climate Center GHRC Web Curator: GHRC Web Team Last update: Tuesday, 12-Jun-2007 16:56:54 CDT If you have trouble viewing or navigating this page, please contact GHRC User Services. U.S. Government Compliance report.