Everything space & RF. Amateur radio operator (EA4GPZ / M0HXM). PhD in Mathematics from @Matematicas_UAM. he/him
Tres Cantos, España
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New blog post: Decoding the Roman Space Telescope. On August 31 I observed the Roman telescope S-band telemetry with the Allen Telescope Array some time after launch. This post is a summary of the observation, including the telemetry decode and a preliminary analysis.
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In this recording, Roman is transmitting 19.5 kbaud PCM/PSK/PM with a subcarrier of 1.7 MHz, using CCSDS concatenated coding with 8 interleaved RS codewords, and AOS frames. I have managed to interpret the Space Packet timestamps and find some ASCII strings.
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New blog post: On matched filtering in the presence of carrier frequency offset. In this short maths note I explain how to tweak a matched filter to improve the SNR when there is carrier frequency offset.
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I close with some remarks about usage in practice. When the frequency grid spacing is narrower than the inverse of the number of samples, the conventional matched filter performs quite well and the DPSS-windowing improvement is small. For larger spacings it provides a minor gain.
ALT A plot that compares the average SNR loss with respect ideal filtering of both the classical matched filter and DPSS-windowed matched filter, in terms of the frequency grid spacing.
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New blog post: X-engine correlator on a Ryzen NPU. A few months ago I posted about the basics of NPUs in Ryzen AI chips. I wanted to tackle a real-world problem to get more experience, so I've implemented an X-engine correlator like the ones used in radio astronomy.
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Next I consider the data flow through the whole NPU array. This leads to a design of the Ethernet packets that the X-engine ingests. There is a tradeoff between having the data in the order that the X-engine prefers and having it in an order that is easy to generate in the PFBs.
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Finally I go into the technical details of how to implement all this with the mlir-aie framework, and the challenges to program the DMA engines in the way we want. I close with some benchmarking results.
Read more: destevez.net/2026/08/x-engin…
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As we're seeing more and more issues and PRs that use LLMs in some way, the gr-satellites project is considering adopting an AI policy to have clearer guidelines of what to expect and how to proceed. If you have strong thoughts, join the discussion in github.com/daniestevez/gr-sa…
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New blog post: Tianwen-1 safe mode telemetry. Peter from @amsatdl noticed that a few days ago Tianwen-1 was transmitting in safe mode. Here I analyze the telemetry signal, which is only 32 baud (16 bits per second). destevez.net/2026/08/tianwen…
ALT A screenshot of a GNU Radio GUI that shows the spectrum of the signal and a time domain plot of the demodulated symbols.
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This Sentinel-2 infrared image from yesterday shows the extent of the Madrid wildfires, which are now stable and do not show any smoke in satellite imagery. The false colour map shows two shortwave infrared bands (B12 and B11) in red and blue, and near infrared (B8) in green.
ALT A false colour satellite image that shows the western half of Spain and all of Portugal. The tweets describe how the false colour map works and what fires can be seen. Besides that, it is noticeable the higher amount of vegetation in the north and northwest part of the Iberian peninsula, and also in a few small regions in the interior.
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Burnt areas appear in dark red or purple, due to the dryness causing lower water absorption in shortwave infrared, and higher absorption in near infrared caused by soot. Healthy vegetation appears in green due to the high reflectance of leaf cellular structures in near infrared.
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