HRPT
Much more data that LRPT. Everyday there are more and more satelites with HRPT transponders.
Frequency: 1.7 GHz.
HRPT satellites
There are currently four satellite constellations with operational HRPT payloads;
- 3x POES (2 operational, 1 with limitations)
- 2x Meteor-M (1 operational, 1 with limitations)
- 2x MetOp (2 operational)
- 2x FengYun-3 (2 operational with limitations)
HRPT frequnecies:
- NOAA-15: 1702.5 MHz
- NOAA-18: 1707.0 MHz
- NOAA-19: 1698.0 MHz
- Meteor-M N2: 1700 MHz
- Meteor-M N2-2: 1700 MHz
- MetOp-B: 1701.3 MHz
- MetOp-C: 1701.3 MHz
- FengYun-3B: 1704.5 MHz
- FengYun-3C: 1701.4 MHz
Hardware requirements
Computer
A good consideration is to leave your computer far from the antena, that is at least 5 meters.
Receiver
The minimum requirements for an SDR receiver are that it has to be able to tune up to 1.7 GHz and sample 2.6 MHz of spectrum.
Amplifier
Mandatory to use a LNA. While a wide-band LNA such as the LNA4ALL or the SPF5189z works just fine on 1.7 GHz, due to its wide-band nature it can often result in very strong interference from the lower bands. This is why a filtered LNA is usually used for all kinds of microwave reception. Recommended amplifiers for this operations are Sawbird amplifiers from Nooelec. The Nooelec Sawbird GOES is a low-noise amplifier with an integrated 1650 - 1720 MHz bandpass filter.
Dish reflector
The dish size recommended by official HRPT documentation is up to 2 meters, however for amateur use a typical 70 - 80cm offset dish is perfectly usable. WiFi grid reflector dish antennas that are often reused for HRIT reception, which happens to be in the same frequency range as HRPT. And indeed such an antenna would also be usable for HRPT, provided that it is big enough.
Dish feed
The helical feed consists of only two wavelength-dependent parts; the reflector and helix itself. These can be as simple as a thin sheet of metal and solid-core copper wire.
It is important to mention that after the signal is reflected in the dish the polarization is inverted.
From the article, my recommended concrete dimensions for a HRPT helical feed for a standard offset dish would therefore be;
- 5.5 turns
- 56mm diameter
- 25mm turn spacing
- 130mm reflector diameter
- LHCP
In some cases a “matching strip” is also added to the first quarter turn of the helix, which is in the form of a curved copper plate soldered to the helix conductor and running parallel to the reflector. This is to further decrease the impedance of the helix to bring it closer to 50 ohms. I personally don’t include a matching strip in helical feeds, as they are only used for receiving and work “good enough” without it.
Feed reflector
The feed reflector should be at least the size of 3/4 of a wavelength.
Decoding
With the sdr software you get your baseband signal.
Currently there are only two programs that I would recommend for people starting out with HRPT reception;
The postprocessing is made with LeanHRPT-Decode.