HRIT and LRIT Geostationary Weather Satellite Image Reception
Key Words: GOES, Geostationary Weather Satellite, HRIT, LRIT
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Geostationary weather satellite image reception is more challenging than APT weather satellite image reception, but can be achieved well using an SDRplay RSP2 as described here. Before getting started in putting together a receiving system for HRIT and LRIT images, it is a good idea to go through this article and get a good idea of all of the software, components, and related expenses. The HRIT and LRIT images available from the GOES 13, GOES 14, GOES 15, GOES 16, and similar satellites are really spectacular. The file size limitation for posting images on this site significantly reduces the available resolution. Complete images can be 40MB in size.
The above is a GOES 13 LRIT image received with the loop Yagi antenna and USA-Satcom XRIT decoder software; the gray-scale image has been colorized using Adobe Photoshop™.
Part of the challenge in setting up a geostationary weather satellite image receiving system is in determining where your position is in relation to the various geostationary satellites. One way to get an idea of the satellite’s position is to apply Orbitron software and select the geostationary satellite of interest and look at its position in relation to where you are. This will help you visualize approximately where to point the antenna. Orbitron software is available here: http://www.stoff.pl/.
In a typical setup, a 1 m diameter parabolic reflector antenna or equivalent (20dbi to 22dBi gain) works well. However, if you are nearing the outer fringes of the reception area, you may need up to a 2.2 m diameter parabolic antenna or equivalent (around 28dBi gain). To give you a rough idea, a 1 m wide parabolic grid reflector antenna such as the L-Com Hyperlink Brand HG1922EG having 22 dBi gain has been used with good results receiving GOES 13 LRIT and GOES 16 HRIT images from areas across the continental United States. The loop Yagi antenna described here and in the prior HRPT image reception article also works quite well (viewtopic.php?f=5&t=2624) for receiving GOES HRIT and LRIT images. With either type of antenna, you will need a good LNA such as the TriQuint/Qorvo TQP3M9037-PCB evaluation PCBA which provides approximately 21dB gain with a noise figure of 0.36dB when operating in the 1.69 GHz range. The LNA in the image below has been modified to apply a 10uH inductor 220 mA (PN 9250A-103-RC) and 33uF 25VDC capacitor (PN TAP336K025SCS) to supply power via the coaxial cable from the RSP2 using the RSP2’s BIAS-T feature on Antenna Port B. The TriQuint TQP3M9037-PCB evaluation PCBA only requires around 47mA at 5VDC. Operation off of the RSP2 Bias-T power can be used, if a band pass filter is not needed in your area. Be sure to use flexible (to allow the antenna mount to move properly), low loss cable, such as LMR-240 to connect the LNA (and filter, if a filter is used) which is used to go the short distance to the RSP2 (or a line driver, if the RSP2 will be mounted far away from the antenna).
If you live in an area with high levels of terrestrial interference near the frequency of interest, you may wish to further employ a filter such as a Sysmocom or similar L-Band cavity filter with a pass band of 1525 MHz to 1750 MHz. If you place a filter between the LNA and the RSP2, you will need to provide 5VDC power directly to the LNA and may not wish to apply the Bias-T modification described above, since the filter will not pass the DC voltage through.
The Meade DS2090AT telescope mount with a 497 controller was repurposed for use as a tracking system and mount for pointing a loop Yagi antenna to geostationary and orbital satellites. The L-Com antenna described above will be too heavy and bulky for proper use with the Meade DS2090AT mount, so a different mount would be used with the L-Com antenna. If you use a loop Yagi and the Meade DS2090AT, be sure to obtain the latest DS2090AT version which has a blue band around it showing the position rather than a black band. Older versions of the mount may not work as well without some modification for this application (they may slip in vertical movement, given that the loop Yagi antenna having 26 director elements is near the maximum out-of-balance weight for the mount – if it should slip and tightening does not solve the problem, pull the vertical control portion apart and insert a rubber washer such that it is between the friction plate and the original gripping section; alternatively, you may be able to add some non-metallic weight to the back of the boom to better balance the antenna in the mount). Given that the diameter of a 90 mm telescope tube is near that of the loop Yagi in the 1.69 GHz range and the antenna weight is comparable to that of a telescope tube, making use of a used telescope mount capable of tracking satellites worked well in this instance. Meade Instruments has downloadable software on its web site to allow uploading the most recent versions of software and TLE (satellite data) files to the 497 controller using an RS-232 serial cable. Refer to the Autostar™ Software Updater. Additionally, Meade has downloadable Autostar™ Suite software to enable using the DS2090AT mount to point to any position in the observable sky for geostationary satellite image reception as well as to track orbital satellites passing overhead. With the Meade DS2090AT telescope mount and 497 controller, once the setup has been initialized, you can point the loop Yagi antenna directly to the geostationary satellite of interest.