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Tianwen-1 safe mode telemetry
On 2026-08-02, Peter Gülzow, AMSAT-DL's president, noticed that Tianwen-1 was transmitting very low rate telemetry, in contrast to the usual 16 kbaud telemetry. This is typical of a safe mode configuration, since it allows decoding even when low gain ante
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ORI's lunar descent CTF
Open Research Institute has recently published the solutions for a Lunar Descent CTF that they ran at BSides San Diego 2026. The CTF revolves around the Ka-band radio altimeter used by the Chandrayaan-3 lunar lander. The CTF includes a simulation of the r
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Tianwen-2 low data rate telemetry
Thomas Telkamp has shared with me an IQ recording of the Tianwen-2 telemetry downlink made with the Bochum 20 metre antenna on June 8. This is part of an ongoing effort led by Peter Gülzow, AMSAT-DL's president, for closely monitoring Tianwen-2's operatio
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PLL coefficients for rate-only feedback
A couple years ago I wrote a post about the paper Controlled-Root Formulation for Digital Phase-Locked Loops, by Stephens and Thomas. In this paper, the authors study digital PLLs by studying the transfer function in discrete time, rather than doing any c
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