AOS - Acquisition of Signal. The time at
which a satellite rises above the local horizon. For a LEO
satellite, it's passage across the sky will take around 15 minutes. The
satellite's setting time is known as Loss of Signal,
APT - The simple analog mode of NOAA image transmission is known
as Automatic Picture Transmission, or APT.
APT images have a ground resolution of around 4km. NOAA
transmit a higher resolution digital mode known as High Resolution
Picture Transmission (HRPT), where ground
small as 1km may be observed. By a slightly confusing
coincidence, the building
where our satellite receiver is housed is known as the Automated Patrol
Telescope , more usually, "The APT".
Australian EST - or Eastern Standard Time,
is used throughout most of eastern Australia and Tasmania. During
Austral wintertime, EST = UTC
+ 10 hours, and during summertime Eastern Daylight Time
(EDT) = UTC + 11 hours. The date at which Australian daylight
saving starts and stops can be found at this useful site.
Carrier - An unmodulated radio
wave, what you hear if you tuned into an AM or FM radio station, and
nobody was talking.
Footprint - How much of the Earth a satellite can see is
dependent on the satellite's altitude. NOAA polar orbiting
satellites orbit at an altitude of ~800km, and from that height can
view a circle of the Earth
around 6000km wide. The area of the Earth that can be seen by a
satellite, is known as the satellite's footprint. If one
whereabouts of NOAA 12 and NOAA 15,
the footprints are indicated by the circles drawn around the satellite.
one checks the current
whereabouts of NOAA 17 , the image presented shows only
NOAA-17's footprint, and monitoring this particular image demonstrates
just how much of the Earth is covered by ocean.
HRPT - See 'APT' above
LEO - Most Earth orbiting satellites actually fly fairly close
the Earth's surface, with altitudes typically between ~300 - 2000km.
orbits are known as Low Earth Orbit, or 'LEO'.
satellites into higher orbits such as Geostationary and Molniya,
vastly more rocket power and complication, and hence most satellites
placed low down, often skimming just above the Earth's atmosphere.
MCIR-precip - WXtoImg's Map
Coloured IR enhancement (used for nighttime passes),
highlighting of rain potential cloud.
Spectral Analysis enhancement (used for daytime passes
with solar elevation >15°), with coloured
highlighting of rain potential cloud. For
further technical details of MCIR and MSA image
enhancements, see the WXtoImg User's
Maximum Elevation - The NOAA satellites are on near-polar orbits
(orbital inclination ~98.6°), meaning that they will normally be
observed to track along a North-South line, southbound in the morning
and northbound in the evening. An observer will normally notice that
they reach the maximum angle above the horizon when passing the
due-east or due-west direction.
Sucker Hole - Astronomer's slang for a hole in the cloud which
closes up, just at the moment when a telescope has been laboriously
repositioned to look through it.
UTC - or 'Universal Time' = Greenwich Mean Time
(GMT) for all practical purposes. The Universal
Time at which you loaded this page was: UTC
VHF - Very High
Frequency. Radio frequencies within the range 30 to 300
Megahertz. For example, ordinary Broadcast-FM stations transmit
somewhere between 88 to 108 Megahertz, and are therefore 'VHF'.