My interest in weather is mainly focused on the technologies required to receive real-time weather images from satellites. I use Victoria University Wellington's meteorological forecasting pages for my long range weather insights.
From the Weather sub-menus choose WXTOIMG to see thumbnail views of three days of current and past weather images recorded as from early 2018. Click on a thumbnail to get a new window to pop up with a larger view of the weather image. Close the pop-up to return to the WXTOIMG page. Predicted satellite passes are listed at the bottom of the page. When you view this page I may still be recording satellite data, but also I may have moved on to other interesting topics, so it is a toss-up about whether the information on the wxtoimg page is current or not.
From the sub-menu choose MetVUW (Meteorology - Victoria University Wellington) to access their long range forecast service. I commonly select the 10-day forecast images which give 6-hourly snapshots of what the weather will be doing in New Zealand. I use this to support my mountain hiking activities.
In 2018 four polar-orbiting satellites provide receivable VHF (very high frequency) direct weather picture broadcasts. Three are American, being NOAA-15, NOAA-18 and NOAA-19 (run by the National Oceanic and Atmospheric Administration) which all pass analog data in an Automatic Picture Transmission (APT) format. This format was introduced in the 1960s, so is considered old in comparison to modern digital techniques, such as that used by the modern fourth weather satellite operated by Russia, Meteor-M2, which uses quadrature phase-shift keying (QPSK).
All four satellites are classed as polar orbiting environmental satellites (POES) meaning their orbit path takes them over the north and south poles and they travel close to the earth (between 700 - 850 km up) so they have good signal strength compared to the geostationary satellites parked above the equator (which are 35,800 km up). They take between 101 - 102 minutes to circle the earth once. However, as the earth has rotated on its axis during this period, the satellites always observe an adjacent sector of the earth, not the same sector they just been over. In the course of a day they scan the whole earth twice. From New Zealand the four satellites do a series of morning passes coming down from the North Pole and in the afternoon and evening they do more passes, this time rising up from the direction of the South Pole.
Home-built quadrafilar helix antenna (QFH or QHA), a design which gives good signal strength coverage out to the horizon and is circularly polarised which prevents fading losses due to satellite spin-stabilisation.
An RTL-SDR which is a variety of software defined radio. My SDR is the size of a fat USB memory stick and has the power of a very capable purpose-built scanner receiver. It cost me NZ$35 on an online auction site for a new receiver, whip antenna and dipole antenna plus mounting bases.
I use SDR# software to control the RTL-SDR receiver. It is a good choice because software engineers publish add-on modules that allow me to automate my weather satellite reception. The SDR# and module add-on software is free.
I use Orbitron to calculate when the weather satellites are in range, to turn on and off SDR#, and to set SDR# to the correct satellite frequency and bandwidth. I install the software module 'Tracking DDE Client' in SDR# to interface between Orbitron and SDR#. It allows me to set up configuration settings at AOS (acquisition of signal - or satellite) when the satellite rises above my radio horizon, and other settings to close things down at LOS (loss of signal) at the end of the satellite pass. I am assessing a free (cardware) version of Orbitron. I may look elsewhere for a satellite prediction program as Orbitron doesn't allow me enough automatic control over which satellites will activate SDR# when there is more than one satellite overhead. It was better than WX-Track in this regard though.
Virtual Audio Cable:
VAC is used to connect the output of the SDR# to the input of WXTOIMG. It is a cable created in software, so there is nothing to see. But it works great and is free.
WXTOIMG is a very smart program that takes satellite analog audio data (NOAA satellites) from SDR# and converts it to pictures, pushing the finished pictures up to this website. It has a range of processing options and I have selected the 'map coloured infra-red' (MCIR) false colour option, with highlighted precipitation. If no processing is used the pictures appear a muted range of grey and white. MCIR with precipitation gives a stunning view of land, ocean and probable weather storm fronts. I use a licenced version of WXTOIMG.
For Meteor-M2 satellite collection I use Orbitron and the Tracking Client to turn on SDR#'s 'Meteor Decoder' module and the external program 'M2 LRPT Decoder'. Meteor Decoder outputs a broad 'baseband' signal to the LRPT (low rate picture transmission) program which converts the QPSK data to a visible scanned image. It also passes the picture data over the Internet to a database that collects all users weather records for processing and world-wide sharing. In 2018 the global sharing aspect was still being implemented. These decoding modules have been created by dedicated volunteer meteorological amateurs in Russia. Their work ensures the educational aspect of weather satellites remains available as satellites evolve to newer technology. They have named their system AMIGOS after 'Amateur Meteor Images Global Observation System'.
Because the global system has no display component at this time I have work to do to provide local Meteor M2 pictures from my received data. I can do this manually, but I need to automate that process.
The modern USA polar weather satellite system which will supercede the old NOAA satellites disappoints me. There is no longer any ability for amateur or educational direct weather collection as their new system requires purpose built earth stations to download data and a distribution centre to pass the weather information to officially approved users. Their website education content appears to be minimal.
Their first new satellite is named Suomi NPP (National Polar-orbiting Partnership), which launched in 2011 as a 'bridging' service supporting transitioning from old to new systems. The new system is called JPSS (Joint Polar Satellite System) with its first launch in 2017 of JPSS-1, renamed NOAA-20 on successful commissioning in space. JPSS-2, 3 and 4 are scheduled for launches in 2021, 2026 and 2031.
The modern Russian weather satellites in the Meteor-M series replace the older Meteor weather satellites which have mostly failed or been turned off. The first Meteor-M1 satellite in the new series has technical problems, so normally is turned off (March 2018). The third satellite in the series was destroyed during launch along with 18 other satellites on that rocket. Apparently old guidance software had been installed in the rocket instead of the well-tested new software needed for rockets departing the new Russian space launch site. The upper stage and its satellite payload never made it to space and burnt up on re-entry.