CAMEX-3: DC-8 Data Acquisition and Distribution System (DADS) Navigation Data

Table of Contents

1. Introduction
2. Content and structure of the DADS files
2.1 9600/19.2K Baud Block Configuration
2.2 Mission Manager Discretionary DADS input lines
3. Contact Information

1. Introduction

This README file contains information about the content, and structure of the DC-8 Data Acquisition and Distribution System (DADS) Navigation Data files for flights in support of CAMEX-3. These data files were generated on board the DC-8, saved to disk, and downloaded post flight.

2. Content and structure of the DADS files

The DC-8 DADS serial transfer of housekeeping data allows easy access to aircraft data by experimenter-operated computers. The data was transferred at one second intervals with transmission rates of 1200, 9600, and 19.2K baud. The data in these files were the data transferred at the 9600/19.2K baud rate, and are described in detail below.

2.1 9600/19.2K Baud Block Configuration

Data was transferred once per second at 9600 and 19.2K baud in seven 56-character blocks. Each block begins with a unique character identifier and ends with an ASCII carriage return and line feed. The contents of the first five blocks (identifiers C through G) are fixed. The contents of the last two blocks (identifiers H and I) were at the discretion of the Mission Manager and may change from mission to mission and are described in some detail in paragraph 2.2. The total number of characters available every second with this configuration is 392. See the table below for the description of the 9600/19.2K baud serial data blocks.

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. Below is shown an example of the 9600/19.2K block format (with nomenclature shown above) followed by a block of actual data.
 

WWW.W

General

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.
 
 
 

2.2 Mission Manager Discretionary DADS input lines

The contents of two of the seven data blocks transferred from the DADS to experiments at 9600 and 19.2K baud were subject to the discretion of the Mission Manager. The first table below gives the coded readout for the Mission Manager discretionary blocks and the second gives two examples- the first in coded form, and the second with data.

9600/19.2K Baud Discretionary Block Configuration

Identifier	Parameter	Format	Units
H	GPS UT	aa:aa:aa.aaa	hour:min:sec (UT)
	GPS latitude	+/-bb bb.b	degrees & minutes
	GPS longitide	+/-ccc cc.c	degrees & minutes
	GPS altitude	ddddd	feet
	GPS vertical speed	eeeeee	ft/min
	Spare A/D	fff. fff
I	Sun elevation in ground reference frame	ggg.g	deg
	Sun elevation in aircraft reference frame	hhh.h	deg
	Solar zenith angle in ground reference
	frame	iii.i	deg
	Waypoint Latitude	+/-kk kk.k	degrees & minutes
	Waypoint Longitude	+/- lll ll.l	degrees & minutes
	Potential temperature	mmm.m	degK
	Specific Humidity	nn.nnn	g H2O/kg air

 

Mission Manager Discretionary Blocks Example
 

H aa:aa:aa.aaa +bb bb.b +ccc cc.c ddddd eeeeee fff.fff<cr><lf>  I ggg.g hhh.h iii.i j +kk kk.k +111 11.1 mmm.m nn.nnn <cr><lf>  H 01:22:45.105 +34 25.0 -122 03.0 28000   1400   0.000<cr><lf>  I  12.5  11.3  77.4 1 +40 00.0 -130 30.0 311.0  5.882 <cr><lf> Index:  01234567890l234567890l23456789012345678901234567890123<cr><lf>

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

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 10:24:03 CDT If you have trouble viewing or navigating this page, please contact GHRC User Services. U.S. Government Compliance report.