AOS - Acquisition of Signal, when a pass starts.
APT - Automatic Picture Transmission - the analogue
transmission standard used on the 137MHz band from polar orbiting
satellites. A simple omni-directional antenna will pick up these
ASCAT - Advanced
scatterometer, an instrument on Metop.
Ascending pass - satellite pass crossing the equator from south to north.
ASL - Above Sea Level, a height in feet or metres.
ATOVS - Advanced TIROS Operational Vertical Sounder. Data from
multi-channel thermal and microwave sensors carried on the polar orbiters.
By providing multiple channels, some information about the profile of
atmospheric constituents can be derived. "Sounder" implies
looking into the atmosphere at different depths.
AVHRR - Advanced Very High Resolution Radiometer - the 6-channel imaging
instrument carried on the NOAA polar orbiting satellites like NOAA-15 and
NOAA-17. Five of the six channels can be transmitted with HRPT and two
channels with APT.
BUFR - Binary Universal Form for
the Representation of meteorological data. BUFR is the name of a binary
code for the exchange and storage of data. See: WMO
C-band - satellite TV band with a downlink centred on
4GHz. Suffers less from rain attenuation than Ku-band, and therefore
preferred in tropical regions. Used for EUMETCast in Africa.
Channel - typically typically on spectral channel
(q.v.) derived from detecting radiation at a certain well-defined
wavelength. The 12 Meteosat-8 channels are described here.
CLASS - Comprehensive Large
Array-data Stewardship System. An electronic library of NOAA environmental
Descending pass - satellite pass crossing the equator from
north to south.
DVB - Digital Video Broadcasting. A standard for video broadcasting
with variants for cable (DVB-C), satellite (DVB-S) and terrestrial (DVB-T)
methods. The DVB-S system is used for EUMETCast from the Eurobird-9 satellite.
DVB PCI card - DVB satellite TV and data receiver card, installed inside
your computer, used for EUMETCAST reception.
DVB USB Box - DVB satellite TV and data receiver which is external to
(not requiring installation inside) your computer which plugs into a
EARS - European ATOVS Retransmission Service.
Service operated by EUMETSAT which takes data from the polar orbiting satellites
and broadcasts it over EUMETCast. This means that you do not need a
complex tracking antenna and receiver to receive this data.
Eclipse period - twice a year geostationary satellites have periods
in their orbits where the earth eclipses the sun. blocking energy to the
solar panels. The Meteosat Second Generation satellites rely on battery power during
this period, but other satellites may have elements switched off to conserve
EKU - EUMETSAT Key Unit - a USB-based eToken
which plugs into your PC's USB port to allow access to EUMETCast data
streams. You can purchase an EKU from EUMETSAT.
EPS - EUMETSAT
Polar System - the "morning" (local time) polar orbit
satellite, with the "afternoon" coverage being provided by the
US. The satellite is called Metop.
ESA - European Space Agency
responsible for satellite launches.
ESOC - European Space Operations
Centre at Darmstadt in Germany.
EUMETCast - system for sending a digital data stream over a DVB
link. Operated by EUMETSAT, the current broadcasts include data from the
geostationary Meteosat-8 and GOES satellites, ATOVS data from the polar orbiting
satellites, and Rapid Scanning Service data from Meteosat-6. The different
data streams have different PIDs. An EKU is required to access certain
EUMETSAT - European Organisation for the Exploitation
of Meteorological Satellites - operator of weather satellites based in Darmstadt, Germany.
Operates Meteosat-5, 6 & 7 and the Meteosat-8 satellites, and allows amateurs
and educational users free access to the real-time data.
FTA - Free To Air. You may have seen this on the
TechniSat equipment info sheets - these are unencrypted (DVB) TV channels [Frei-Sat
GEO - the Group for Earth Observation.
GeoSatSignal - my geostationary satellite data processing program.
Geostationary - satellites with an orbit keeping them at a fixed point above the
equator. This includes many weather and telecommunications
satellites. The orbital height is about 36000km above the earth.
GMS-5 - Japanese geostationary satellite covering Asia and Australasia
- replaced by MTSAT-1R.
GOES - Geostationary
Operational Environmental Satellite. The US geostationary satellites
managed by NASA and NOAA, comprising GOES-12 at 75°W and GOES-10 at 135°W
covering the continent of America. They are also providing temporary
coverage of Asia/Australia from GOES-9 replacing GMS-5.
GPS - global positioning system, a collection of satellites in
12-hour orbits allowing accurate location and time determination.
GRIB - General Regularly-distributed Information in Binary, a binary data
format used for information which is on a grid like a map projection. See:
Hot Bird - a cluster of satellites used for TV transmissions, including
the DVB used by EUMETCast. There are 5 satellites at the 13 degrees East
EUTELSAT Hot Bird location - Hot
Birds 1, 2, 3, 4 & 6. Hot Bird 5 crashed on launch.
HRIT - High Rate Information transmission - digital
transmission standard for geostationary weather satellites when the data rate
exceeds 128Kbit/s. There is an HRIT data channel on the EUMETCast service.
HRPT - High Resolution Picture Transmission - digital transmission standard for
polar orbiting satellites.
HRPT Reader - my HRPT decoding and display program.
HRV - High Resolution Visible channel. A channel on Meteosat-8 with a
broad spectral response providing 1km resolution at the satellite
sub-point. The complete image from the HRV channel would be 11136 x 11136
pixels, but not all of that data can be transmitted.
HRV Window - because all the data from the HRV channel cannot be
transmitted with the bandwidth available on the Meteosat-8 satellite-to-earth
downlink, only half the available scan width is used. The portion of the
earth where this scan is centred can be varied between the southern and northern
parts of the scan. Typically, the southern part of the scan covers Africa,
and the northern part of the scan covers Europe and the Mediterranean.
Inclination - the angle which the satellite's
orbit makes to the earth's equator. Ideally, a geostationary
satellite would have an inclination of zero degrees, but in reality
towards the end of the satellite's life there is not enough fuel to make
the minor orbit corrections required for zero degrees inclination, and the
inclination increases. In June 2004, for example, the inclination of
Meteosat-5's orbit was nearly 7°.
Kepler data - data describing the orbit of a
satellite, whether polar orbiting or geostationary. As opposed to a
precise orbital model, Kepler data is intended to be used around the time that
it is measured. This allows the data and the calculations to be
simplified. Depending on the satellite and your application, the Kepler
data (sometime called "Keplers") will be valid for some days or weeks
ahead. CelesTrak.com is a good
online source, and you will need to register at Space-Track
for access after 2005 April 01.
KOZ - Keep-Out zone - with GOES satellites, the region where the sun might
damage a sensor if the image were allowed to be within the field of view. More.
Ku-band - satellite TV band with a downlink centred on
12GHz. Suffers more from rain attenuation than C-band. Used for
Eumetcast in Europe.
Level-0, level 1,0, level 1.5 - processing levels in satellite
data. Level-0 or level 1.0 usually refers to the raw satellite data,
straight from the sensor. Level 1.5 data may have been processed to a
specific gain setting (so that the sensor count to radiance level is known) as
may have been geo-located so that the pixels appear as if from a perfect sensor
(in the case of geostationary satellites). Level 1B, 1C, 1D and 2 are also
terms you may meet.
LHCP - left-hand circular
polarised, type of radio-frequency signal transmitted for backup HRPT
LNB - Low Noise Block. The chunk you will see at
the focus of your satellite TV dish, which comprises blocks to convert the
Ku-band signal down to a more suitable frequency for cable transmission to your
PC. Typically there will be an RF-amplifier, mixer, and dual-frequency
local oscillator - the front-end of a superhet receiver. As the satellite
transmissions include both vertically and horizontally polarised signals, the
LNB will include polarisation switching capabilities.
LOS - Loss of Signal, when a pass ends.
LRIT - Low Rate Information transmission - digital
transmission standard for geostationary weather satellites when the data rate
does not exceed 128Kbit/s. There is an LRIT data channel on the EUMETCast
Meteosat - Meteosat 5, 6, and 7 are the current
geostationary satellites operated by EUMETSAT. Met-5 is over the Indian
Ocean from 63°E, Met-6 provides rapid scanning of Europe from 10°E, and Met-7
provides coverage of Europe and Africa from 0°.
Metop - Metop is a series of
three satellites to be launched sequentially over 14 years, starting in 2006,
and forms the space segment of EUMETSAT's Polar System (EPS).
MODIS - a higher resolution sensor than the AVHRR, currently carried on
the AQUA and TERRA satellites. More
MSG Animator, MSG Data Manager - my software
for handling MSG data.
MSG - Meteosat Second Generation. The first generation
includes the still-operational Meteosat-5, 6 and 7 satellites. The MSG
more channels and higher resolution. There is a Meteosat Third Generation
(MTG) satellite series at the very advanced planning stage. Meteosat-8
(formerly MSG-1), the
first satellite in the series, is now operational and will replace Meteosat-7.
MSG-2 was launched in 2005 and will likely be called Meteosat-9 when
MTG - Meteosat Third Generation, the follow-on to MSG.
MTP - Meteosat Transition program - those EUMETSAT satellites required to
provide coverage between the end of life of Meteosat-4 and the start of
operation of the Meteosat Second Generation series.
MTSAT-1R - Japanese geostationary satellite covering Asia and Australasia.
Multicast - data packet intended for reception by multiple
NASA - National
Aeronautics and Space Administration (US).
NOAA - National Oceanic and Atmospheric
NTFS - New Technology File
System. Microsoft's advanced, more robust and more reliable file
system which can be used with Windows NT, 2000 and XP.
PID - Packet Identifier - the label attached to different data streams in a
DVB system. Your PC can respond to one or more PIDs, allowing you to
control what data you receive from all the data which may be available.
POES - Polar
Operational Environmental Satellite. The US managed polar orbiting satellite
Polar orbiter - satellite in a polar orbit, typically successive satellite
passes are 100 minutes apart, and pass progressively further west. Your
location will get one northbound (or Ascending) and one southbound (or
Descending) pass per day.
QFH/QHA - Quadrifilar Helix Antenna - antenna with
twisted elements for VHF APT reception. Here is an
RHCP - right-hand circular polarised,
type of radio-frequency signal transmitted for HRPT transmissions.
RSS - Rapid Scanning
Service. EUMETSAT are using
the Meteosat-6 satellite to provide images every 10 minutes over Europe.
Data is transmitted via the EUMETCast service.
RX - Receiver
SAA - Satellite Active Archive - library of NOAA data
now replaced by CLASS.
SAF - Satellite Application Facility. A EUMETSAT
group of experts who define the algorithms to produce derived products from
satellite data. SAF may also refer to the software used to run the
algorithms. An operational example is the Sea-Ice SAF who produce data
from the polar orbiting satellites, and whose data is transmitted as part of the
EUMETCast data stream.
SatSignal - my APT decoding program.
SEVIRI - Spinning
Enhanced Visible and Infra-Red Imager - the scanner used in the MSG
satellites to convert visible and infra-red radiances into electrical signals.
Single-chord operations - with GOES satellites, a way of maintaining
location accuracy even when the moon or sun enters the earth location sensor's
field of view. More.
Spectral channel - that range of the electromagnetic spectrum to which a
particular channel is sensitive. A given satellite will have sensors
covering multiple spectral channels. For example, the earth emits its
natural radiation with a maximum energy around the 10µm wavelength, so to
measure the earth's temperature one would use the 10µm channel. The sun
emits most of its energy in the 0.4µm to 0.7µm region, so to measure things
like surface reflectivity, spectral channels in the 0.6µm region might be used.
12 channels on Meteosat-8.
SSP - Satellite sub-point. That point on the earth's surface which
is directly below the satellite.
TIROS - Television Infra Red Observation Satellite
Transponder - a device for re-broadcasting from a
satellite, data which has been sent up from a ground station. A
transponder may be as simple as a receiver shifting the received signal to a
different frequency followed by a power-amplifier. A typical broadcasting
satellite will carry many transponders, with some spares to allow for in-orbit
VPN - Virtual Private Network. For
accessing your work network from home, a VPN is likely to prevent any of
the network connectivity required by either a EUMETCast receiver or
EUMETCast Data Management PC.
WEFAX - Weather FAX - analogue transmission standard used on
geostationary weather satellites. Will be progressively replaced with LRIT.
WMO - World Meteorological Organisation
WX - weather
WXtrack - my satellite orbit prediction and tracking program.