Equipment Setup and Flight Path
This directory provides selected images from the 1998 FAST
conjugate aircraft flights flown from Fort Wainwright,
Alaska. A Sabre-60 was equipped with an all-sky camera
and 2 narrow-field cameras to provide auroral coverage
along the FAST track with higher spatial resolution.
The narrow-field cameras were in fixed mounts aligned
along the longitudinal axis of the aircraft covering a
roughly 60x20 degree rectangular area. All cameras were
low light level TV systems recording on video tapes at
30 frames per second.
The cameras were all installed with the longer dimension
along the aircraft axis and with the forward direction towards
the right of the screen. Thus, if the aircraft is northbound
north would be to the right and west at the top of all images.
If flying south, north would be to the left and west down.
The narow-field camera elevation angles relative to the
aircraft longitudinal axis and their field of view (all
values in degrees) are:
Forward camera: el= 68 FoV= 29x22
Aft camera: el= 112 FoV= 29x22
The flightpath for each flight was calculated based on the
predicted FAST ephemeris. The position of FAST was
traced using IGRF95 (no external terms) to an altitude of
100 km. Then a position at flight altitude (~13 km) would
be calculated such that the 110 km conjugate would appear
in the magnetic zenith (i.e. the 110 km magnetic field tangent
direction would be used to detemine the aircraft position).
The airplane would be positioned along this path and under the
aurora as FAST passed over the aircraft from the north.
Because the FAST track was not along the magnetic meridian,
the magnetic zenith would be off to the left or right relative
to the direction of the flight/FAST path. At times it would
even be outside the field of view of the narrow field cameras.
We compensated for this by adjustments in flightpath and
flight altitude, and the FAST conjugate was never outside our
field of view.
The FAST ephemeris given in this dataset is the final actual
observed ephemeris as provided by the Berkeley group (Dr. C.
Chaston). The aircraft's position as a function of time was
recorded by multiple GPS units onboard the aircraft. One GPS
system was integrated with our video equipment recording time
and position on the video and sound tracks, and one system
logged time and aircraft position on a laptop computer.
Flight dates and times of conjunction
The times and positions at conjunction were determined post-mission
by comparing the actual FAST conjugates with the aircraft GPS
positions. The dates and times are in UT. Aircraft positions are
in geodetic lat (N), long (E), alt (km). "Dir" is the direction
of the aircraft along the FAST conjugate path (N = north-bound;
S = south-bound). Finally, the 3-hour Kp value is provided to
give an indication of overall activity:
Date Time Aircraft lat,long,alt Dir Kp
01/25 09:07:39 71.46 -157.43 10.68 S 1-
01/26 09:33:04 68.70 -162.84 10.84 S 1-
01/27 07:42:20 68.36 -136.55 10.29 S 2+
01/28 08:02:51 72.24 -146.36 11.01 N 0+
01/29 08:26:27 71.88 -153.09 10.85 S 1+
01/30 08:50:11 71.36 -159.99 10.77 N 3
01/31 09:13:52 70.91 -167.12 10.74 N 2-
02/01 07:24:31 68.83 -139.17 10.79 N 3-
02/02 07:45:48 71.53 -148.14 11.07 N 1
02/03 08:07:46 73.27 -157.02 10.84 N 0
02/04 08:34:44 68.67 -160.83 10.92 S 2-
02/05 06:44:31 67.51 -134.20 10.91 S 0
02/06 07:04:32 71.87 -143.79 10.91 S 1-
Data Types
The data contains images from all flights together with other
supporting information (FAST ephemeris, Aircraft GPS data, and
magnetic data indicating auroral activity levels). The data are
stored in directories covering each flight (i.e. Jan25, Jan26,
Jan27,....., Feb06).
Position data:
1.FASTxxxx.
FAST ephemeris in UT covering about 10 minutes
around conjunction. Table gives satellite location in
geocentric lat,long and altitude above mean equatorial
Earth radius, magnetic local time, and 100 km altitude
conjugate position in geodetic lat,long. The conjugate is
calculated using IGRF95 with no external field.
2.ACxxxxxx.
Aircraft position (geodetic) and UT time for about 10
minutes around conjunction.
Image files:
All images come in Targa (.TGA) and Gif (.GIF)
formats. We have recorded 12 images from the all-sky
data at 10 s intervals around conjunction
(AChhmmss.TGA and AChhmmss.GIF, where hh, mm and
ss are the UT hour, minute and second of the image. The
conjunction time is when FAST passes (nearly) over the
aircraft. Since the magnetic zenith is not overhead,
we have adjusted the time for the selected images.
The time for magnetic zenith crossing is about 4 s
before or after (depending on flight direction) the
conjunction listed above.
One image from each of the narrow field cameras is
provided. The times for the selected images are such
that the FAST ionospheric conjugate is in the image
for both the forward (FDhhmmss.TGA and .GIF) and aft
(RRhhmmss.TGA and .GIF) cameras (about 10 sec
prior to and after the conjunction times).
Also included in this year's (1998) images is one allsky
image (AThhmmss.TGA and .GIF) with the FAST conjugate
trajectory at 100 km printed on the image. This
allsky image is at the conjunction time.
________________________________________________________
FAST Aircraft Data (Jan 25-Feb 06, 1998)
H.C. Stenbaek-Nielsen and T.J. Hallinan
Geophysical Institute
University of Alaska
Fairbanks, AK 99775-7320
907-474-7414
hnielsen@gi.alaska.edu
|