These US Satellites from the National Oceanic and Atmospheric Administration (NOAA) are operating in the 137MHz and 1.7GHz bands. They fly on polar orbits at about 850km above the Earth's surface and their orbital period is about 100min.

These sateliites are transmitting continuously in two modes : APT and HRPT

APT (Automatic Picture Transmission) is the easiest  way to receive these sats. The transmission is done in the 137 MHz band in FM and can be received with a simple VHF Receiver with a bandwith at least of 30KHz. The receiver's audio output is applied to the PC soundcard input.

Several free software can decode the images and apply a postprocessing to colorize the pics. Indeed, the satellites are sending images in black and white visible light as well as infrared light. Postprocessing allows to emphasis different information like rain, vegetation, water temperature, and so on...

At the time I'm writting this article, there are 3 NOAA satellites still active : NOAA 15, 17 and 18.

Sound of an APT transmission : NOAA17_2008_08_10_20h46.wav

Equipment

♦ Receiver

There are differents ways to receive NOAA pictures. Several receivers are suitable and you can easiliy build your own with few electronic components in the 137MHz band. However some commercial equipment are able to receive both the 137 and 1.7 GHz band like the AOR AR5000, ICOM IC-R8500, ...

The discriminator output must be used to avoid the audio filtering usually implemented on such receivers. This discriminator output feeds the PC soundcard line input. It can be a direct connexion or using an isolating interface.

♦ Antenna

Even a vertical 2m band antenna enables you to receive the NOAA sats in APT mode. However it's not intended for and the results may be poor. In APT mode, a simple omnidirectional antenna with a wide vertical lobe is suitable : QFH (QuadriFilar) and Turnstile are the best ans easiest solutions to implement. Many websites are explaining how to build your own from scrap for few dollars or euros. Just google it ! A dedicated 137 MHz preamp may help but it can work without it.

For HRPT modes it's an other story. It requires a small dish with a L-band feed. Some logper antennas may suit. A preamplifier is needed too. As HRPT is transmitted in the 1.7Ghz band, you may need a LNC (Low Noise Converter) to downconvert the 1.7Ghz to 137MHz band for instance. Thus you can use a simple 137MHz receiver both for APT and HRPT, even if it's not able to receive L-band.

Of course, if your are using a dish, it means as the beam is very narrow that you have to 'follow' the satellite. It means motorized dish with satelittes tracker ! It's not so complex to do but you need to get extra equipment...

♦ Software

There are many freewares or sharewares allowing to decode and postprocess the pics from NOAA sats. For instance JVcomm32 or Satsignals are running well.

Personnaly I'm using the excellent WxToImg which decodes and display the pics, predict sats position, can control the receiver as well as antennas rotors and publish automatically pics on your website !  This is an all-in-one package that works fine even if you don't contribute to the author. However you will get further functions by registring.

My simple NOAA station :

At the moment (August 2008) I'm able to monitor only APT mode. The motorized dish is under construction. I will update these pages when I'll be ready for that.

Some pictures received :

Normal picture received from NOAA17. On the left the visible light image and on the right the infrared light image. Pictures have been reduced and quality decreased for publishing...