SeaSpace TeraScan 1.5M, Operation And Maintenance Manual

Page: 106 / 232

90
SeaSpace Corporation
7.1 C
AUSES OF
L
OSS OF
P
ASS
D
ATA
The following conditions can cause loss of pass data. Some conditions will cause a gradual loss of data and only
for some satellites; other conditions will cause a complete loss of data on all satellites. Perform the checks listed
below in sequence before examining the hardware for failures.
7.1.1 Gradual or Temporary Loss of Data
a. Drift in system clock:
Check that the system time service is operating correctly.
Remember to verify correct date and time since the system operates on GMT time (UTC) (Zulu)—
not local time.
b. Old orbital elements:
One or more satellites will show increasing dropouts as the orbital elements get older. Update
orbital elements. Elements as old as five days may start to cause loss of data.
c. Obstruction:
The antenna is pointing at an obstacle that blocks reception. The antenna will continue to track
even if data is not received.
d. Incorrect antenna location on earth:
Use
whereami
or
newsite
to verify or set the correct location.
7.1.2 Complete Loss of Data
a. Incorrect Time:
Passes are tracked, but no data is received. Use
sunclock
, ntp (Acutime Gold GPS only), or
manually enter date and time.
b. Incorrect orbital elements:
Invalid orbital elements for one or more satellites. Enter new orbital elements.
c. Invalid site location:
The system thinks it is located at a different point on the earth. Use
whereami
or manually locate
the system using
newsite
.
d. No passes scheduled to run:
Schedule passes.
e. Antenna does not point in the proper direction. (See Section 7.2.4 on page 92 for diagnostics.)
f. Antenna tracks properly but no data is received. The RF equipment may not be functioning.
(See Section 7.2.5.1 on page 98 for diagnostics.)