CAMEX-4 Conically-Scanning Two-look Airborne Radiometer (C-STAR)

Table of Contents

General Information

The Principal Investigator on the C-STAR instrument is Robbie E. Hood of NASA/Marshall Space Flight Center. C-STAR was flown during the fourth field campaign in the CAMEX series (CAMEX-4). CAMEX-4 ran from 16 August to 24 September, 2001 and was based out of Jacksonville Naval Air Station, Florida, and included missions in the Gulf of Mexico, Carribean and Western Atlantic. The experiment focused on the study of tropical cyclone (hurricane) development, tracking, intensification, and landfalling impacts using both NASA-funded aircraft and surface remote sensing instrumentation. Further information regarding C-STAR may be obtained from: http://camex.nsstc.nasa.gov/camex4/instrument_documentation/ampr.pdf.

C-STAR passively measures the faint microwave signals of wind and ocean interactions. The data retrieved by the C-STAR will assist the design of future spaceborne instrumentation which could measure near surface ocean winds with less fabrication costs but greater global coverage than the current instruments being flown on satellites. Accurate global measurements of near surface ocean winds will increase the understanding scientists have of the way the atmosphere and oceans work together to create the Earth's climate. In this experiment, C-STAR was used to help develop a database of tropical storm related wind field information. These data, when combined with other datasets collected, will increase the understanding of tropical storm dynamics.

During CAMEX-4 C-STAR flew aboard the NASA DC-8 aircraft; thus, the ground spatial resolution of the nadir footprints from the nominal aircraft altitude of 10 km is an ellipse which is 2km along scan and 3.5 km along track. A scan consists of fore and aft sweeps separated by hot and cold load passes, and each full scan takes exactly 10 seconds. There are some unused pixels between sweeps of the loads and the earth scenes.

C-STAR is a single frequency four channel passive microwave radiometer which collects data at 37.1 GHz. The four channels are 37.1 vertically polarized (37V), 37.1 horizontally polarized (37H), 37.1 +45 degrees (37+), and 37.1 -45 degrees (37-). The 37V and 37H are collected through one feedhorn system, with the 37+ and 37- collected through a second separate feedhorn system.

The following table lists several of the C-STAR performance characteristics:

Instrument Geometry

The instrument has a 360 degree conical scan centered at nadir. The cone is oriented 45 degrees off nadir.

The Convection And Moisture EXperiments (CAMEX) are a series of field research investigations sponsored by the Earth Science Enterprise of the National Aeronautics and Space Administration (NASA). There were a total of 15 flights that collected C-STAR data, and are listed in the table below. Note, the flight on 8 August was an instument checkout flight in California.

Information about the imagery available for each of the flights in the table below.

Beginning with this experiment, browse images are combined with the data using UNIX 'tar', into daily mission files using a standard UNIX 'tar' command with the following naming convention:

c4dcstar_2001.ddd_010fff.tar where ddd is day of the year, and fff is the unique DC-8 flight number.

A number of files appear once this file is untarred, but they are of three main types. data, and the two separate types of browse images. They are named as follows:

A FORTRAN read program pub_cstar_read.txt is given below. You should copy this program, or pertinent sections of it, into your own source code with modifications as necessary.

========================= beginning of source code ========================

program pub_cstar_read
c
c Example program to read public C-STAR data into arrays. Data file
c must exist in same directory as the program executable. Just a reader
c program that prints out the time and GPS altitude to the screen.
c
c Date and Time are in UTC. Longitudes are negative-west convention.
c TB's and noise are in Kelvin. All other applicable units are metric.
c
c TB arrays are 4-channel X 26 sample in the order: 37V, 37H, 37(+45deg), 37(-45deg).
c F:Forward-scan, A:Aft-scan, at +/- 45 degrees
c
c F. LaFontaine Jan 2002 Release Alpha, SGI/UNIX Fortran-77.
c Please report bugs or errors.
c

logical done
integer i, j, k, NR

parameter (NR=4000)

integer nrec(NR), nmon(NR), nday(NR), nyr(NR),
> nhr(NR), nmin(NR), nsec(NR)

real gps_lat(NR), gps_lon(NR), gps_alt(NR), heading(NR),
> pitch(NR), roll(NR), g_spd(NR), a_spd(NR), noise(4,NR),
> tb37_fore(4,26,NR), slat_F(26,NR), slon_F(26,NR),
> tb37_aft(4,26,NR), slat_A(26,NR), slon_A(26,NR)

open (77, file='GHRC_cstar_flight10_2001262_tbs.txt',
> form='formatted')

print*
print*,' --- Reading GHRC file --- '

i = 1
done = .false.

do while (.not. done)

read (77, 7700, end=777, err=777)
> nrec(i), nmon(i), nday(i), nyr(i),
> nhr(i), nmin(i), nsec(i),
> gps_lat(i), gps_lon(i), gps_alt(i), heading(i),
> pitch(i), roll(i), g_spd(i), a_spd(i),
> (noise(k,i), k=1,4),
> ((tb37_fore(k,j,i), j=1,26), k=1,4),
> (slat_F(j,i), j=1,26), (slon_F(j,i), j=1,26),
> ((tb37_aft(k,j,i), j=1,26), k=1,4),
> (slat_A(j,i), j=1,26), (slon_A(j,i), j=1,26)

write (6, 6000) nhr(i), nmin(i), nsec(i), gps_alt(i)
6000 format (' Time: ',i2,':',i2,':',i2,' Altitude: ',f9.2)

i = i + 1
enddo

7700 format ( i4, x,i2, x,i2, x,i4, x,i2, x,i2, x,i2,
> x,2(x,f9.4), 2(x,f9.2), 2(x,f9.4), 2(x,f9.2), x,4(x,f8.4),
> x,26(x,f9.2), x,26(x,f9.2), x,26(x,f9.2), x,26(x,f9.2),
> x,26(x,f10.5), x,26(x,f11.5),
> x,26(x,f9.2), x,26(x,f9.2), x,26(x,f9.2), x,26(x,f9.2),
> x,26(x,f10.5), x,26(x,f11.5))

777 close (77)

< print*
print*,' --- All data read --- '

return
end

========================= End of source code ========================

Data and browse imagery for the CAMEX-4 C-STAR dataset may now be found on the CAMEX-4 webpage.

To examine other C-STAR datasets

C-STAR datasets are available for other campaigns from the GHRC. Visit our webpage at http://ghrc.nsstc.nasa.gov.

Additional details on the C-STAR data sets can be obtained from the GHRC User Services Office (contact information below), from Ms. Robbie Hood (Principal Investigator), or from Mr. Frank LaFontaine (Co-Investigator). To contact Ms. Hood or Mr. LaFontaine:

Ms. Robbie Hood
Phone: 256-961-7959
Fax: 256-961-7723
E-mail: robbie.hood@msfc.nasa.gov

Mr. Frank LaFontaine
Phone: 256-961-7796
Fax: 256-961-7723
E-mail: frank.lafontaine@msfc.nasa.gov

To order these 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: support-ghrc@earthdata.nasa.gov
Web: http://ghrc.nsstc.nasa.gov/