2026-05-02T18:25:43Z https://yabu.me Daniel Estévez https://yabu.me/npub1u5exd4naj5cq5yfr87dl8c33pswsvl54mpx3gzrcn8paza22genskh4glf https://files.mastodon.social/accounts/avatars/109/245/993/535/607/564/original/05ecc899e74cd497.jpg https://files.mastodon.social/accounts/avatars/109/245/993/535/607/564/original/05ecc899e74cd497.jpg https://yabu.me/nevent1qqs9kdgnv0q2sd6lguhwusj7ddkdmmyrcjenry45dpx6pvs9dkvn7jszyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxw78rs2x New blog post: Analysis of the CAMRAS Venus radar experiment. A deep dive into the Earth-Venus-Earth L-band radar experiment done in March by <span itemprop="mentions" itemscope itemtype="https://schema.org/Person"><a itemprop="url" href="/npub1cuv0mn0tgfr0ehs8aylsxlsfhcf45zldvfqtczm5vjfewja6k7zsrqu7h5" class="bg-lavender dark:prose:text-neutral-50 dark:text-neutral-50 dark:bg-garnet px-1"><span>Dwingeloo Radiotelescoop</span> (<span class="italic">npub1cuv…u7h5</span>)</a></span>, Astropeiler Stockert, the Deep Space Exploration Society, and <span itemprop="mentions" itemscope itemtype="https://schema.org/Person"><a itemprop="url" href="/npub1j94zdu2krsz64ptmag97sqd3w2c2urqrda8egadeeec33u258pzqq8l9ea" class="bg-lavender dark:prose:text-neutral-50 dark:text-neutral-50 dark:bg-garnet px-1"><span>Open Research Institute</span> (<span class="italic">npub1j94…l9ea</span>)</a></span>.<br/><br/>I show how to compute the radar Doppler with SPICE and come up with a Doppler spread model based on an S-band scattering model from Arecibo. I explain why the maximum surface Doppler offset is 8.6 Hz even though the rotational velocity predicts 15.7 Hz.<br/> <img src="https://files.mastodon.social/media_attachments/files/114/369/461/501/691/078/original/8b098a955706008f.png"> <br/> <img src="https://files.mastodon.social/media_attachments/files/114/369/461/798/697/741/original/b20f47f45cdc0f47.png"> <br/> 2025-04-20T08:58:36Z https://yabu.me/nevent1qqsv2r6p395mnk8253yhnw02h0j5mf5ucg8r2s6p4v5jzyqee2k2psqzyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxwg0sgnf In reply to <a href='/nevent1qqszvkxemv9yhqs2yklpd7m9djafx6e227w0kzuqr03fewqmd32vc9s0kygxd'>nevent1q…ygxd</a><br/>_________________________<br/><br/>OSNMA (the Galileo authentication system) is not a paid service. Anyone can use it. But it only authenticates ephemeris data. It doesn&#39;t offer full protection against spoofing. Better protection is given by cryptographic GNSS signals, which are only available to authorized users (i.e., the military, law enforcement, etc.) 2025-02-22T22:31:24Z https://yabu.me/nevent1qqszmfacq0pqvedpvp34lpgax2cgtxzy4pugjcs5gla5sqypmq3r2jqzyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxwem6953 In reply to <a href='/nevent1qqsxks2pv2kveur9te9hdlh4gs8ljy20tgkp67cgc6a465w9lpsl3csh7nc57'>nevent1q…nc57</a><br/>_________________________<br/><br/>it could even happen by accident. One constellation might have a problem that makes the satellites broadcast bad clock and ephemeris data without marking the satellites as unhealthy. 2025-02-22T21:32:09Z https://yabu.me/nevent1qqs2rda7hqq37p5shf7c3a8u89m2f2ujh8ujqrj9nqcrvh5m8u3ghrgzyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxw253tvf In reply to <a href='/nevent1qqsry53059z7l06yd0yj9fca2hxu2n5mej4us6m8953vvqwsm0jmwtsqd306d'>nevent1q…306d</a><br/>_________________________<br/><br/>Bert mentioned one constellation broadcasting &#34;odd data&#34;, but not jamming the others. At least that&#39;s how I understood it. 2025-02-22T21:27:18Z https://yabu.me/nevent1qqs97t5mhd62afx4l76g9ymhsygttskec63dm5smztglws5r48s7ctqzyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxw95ajjd In reply to <a href='/nevent1qqs0kd5rtkwd3yueefa4kdddtvvzkyyeanuxt6qqszhthv97vahrymgz8f9ey'>nevent1q…f9ey</a><br/>_________________________<br/><br/>I&#39;m almost surprised that no one has run the experiment (at least I haven&#39;t seen it in the literature). It looks like an easy way to get a paper published. 2025-02-22T20:33:28Z https://yabu.me/nevent1qqsfqzu9wn8fqs7qw888d84f89r8haudaq44kgevvg27d93auw8yhgczyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxws6ka8w In reply to <a href='/nevent1qqs9kncuskhp4pyd4xemp89qctglyuetn5ne90f09uhz4fg3k09dkggqae5uh'>nevent1q…e5uh</a><br/>_________________________<br/><br/>and before anyone jumps at me, yes, I do understand that the newer GPS satellites don&#39;t even support Selective Availability, but there are many other hypothetical ways of degrading the civilian service. This is mostly intended as a thought experiment. 2025-02-22T19:38:49Z https://yabu.me/nevent1qqs9kncuskhp4pyd4xemp89qctglyuetn5ne90f09uhz4fg3k09dkggzyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxwghzvrc In reply to <a href='/nevent1qqsdhtk5zhn7uhaef73c9m5cq4h2z4k8nye0nrwfce5f5jstd53xpqsssqq3x'>nevent1q…qq3x</a><br/>_________________________<br/><br/>Galileo is great, but people speak about resilience, sovereignty and independence way too soon without thinking about all the technical nuances. Most consumer devices are multi-constellation and use GPS, GLONASS, Beidou and Galileo. They are not very configurable and not very smart. I wonder what would happen if the US decides to turn Selective Availability back again (that&#39;s a mechanism that greatly degrades the civilian GPS positioning accuracy). 2025-02-22T19:37:02Z https://yabu.me/nevent1qqs087a5ljthvrhv0gph7pxr25n73j8u7uu80ccwlmvkfdesd9qllfgzyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxwyh2gp2 In reply to <a href='/nevent1qqs9y2az3escrcrwjzajxn5uee6xmae6e4njrf08slqfclv93gzg89cdtctfq'>nevent1q…ctfq</a><br/>_________________________<br/><br/>It has been a long time since I last used my OSNMA software in this microcontroller (the microcontroller firmware was mostly intended as a tech demo), so I had to search around for my UART TLL to USB adapter.<br/><br/>Check out my galileo-osnma Rust project: <a href="https://github.com/daniestevez/galileo-osnma/">https://github.com/daniestevez/galileo-osnma/</a> 2025-02-15T10:50:35Z https://yabu.me/nevent1qqs9y2az3escrcrwjzajxn5uee6xmae6e4njrf08slqfclv93gzg89czyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxwsu3vs5 Testing again Galileo OSNMA on a small RISC-V microcontroller. [@bob_n6rfm](<a href="https://mastodon.social/@bob_n6rfm">https://mastodon.social/@bob_n6rfm</a> ) wanted some help troubleshooting his system, so I built and tested a known-good firmware image for him. The Galmon data feed is down, so I&#39;m using my own uBlox receiver.<br/> <img src="https://files.mastodon.social/media_attachments/files/114/007/512/262/812/913/original/fde12f5776172bc3.png"> <br/> 2025-02-15T10:50:04Z https://yabu.me/nevent1qqstk0nhsywkdfsppuyagyygfgwautxmp2kzc804lxcte0qx2345ysgzyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxwut2mrp I&#39;ll be all Sunday roaming around FOSDEM. If someone wants to meet, just ping me. 2025-02-02T07:47:18Z https://yabu.me/nevent1qqs2679krng0fthejq48prqrnp2var4tyrfu9wprz84007wyagtn08szyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxwwnnwrj In reply to <a href='/nevent1qqsy0xl34x63sdcuwhayltcunz0cfx9fy8frfvrugnfahf5wkhz6lhgpghxx9'>nevent1q…hxx9</a><br/>_________________________<br/><br/>that is striking to hear. I finished my PhD in 2017, and while I studied I have even gone to the library to try to find a result I needed (some type of inequality) by looking through the books in the harmonic analysis section, figuring from the title on their spine if they might contain something related, and quickly browsing through a few of them. I didn&#39;t find the result I was looking for, but certainly this way of searching you couldn&#39;t do online. 2024-12-13T07:15:00Z https://yabu.me/nevent1qqsxy74t6vg0533d9n437vd7jhrxkz99ucy9t4nvu6zswz073vr2y4qzyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxwcu3c9y New blog post: Decoding Hera. I report about the recordings I did of the Hera X-band telemetry with the Allen Telescope Array shortly after launch and show how to decode them with GNU Radio.<br/> <img src="https://files.mastodon.social/media_attachments/files/113/460/700/337/710/403/original/48a00a66c06b5168.png"> <br/> 2024-11-10T21:08:22Z https://yabu.me/nevent1qqsv87huwrzq44rugl3lxx7s4kt0sqehc925jl2g37hk58afn5r7v9gzyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxwrusc8w In reply to <a href='/nevent1qqswwfeagse8940ewxxce524whrnln6fdkkl2805a5c04dpjxakh29qaqtxe6'>nevent1q…txe6</a><br/>_________________________<br/><br/>The telemetry is AOS frames and Space Packets. The idle packets contain an Easter egg message with the names of the team members. There are many similarities in the telemetry with Psyche, the previous NASA mission.<br/><br/>Read more: <a href="https://destevez.net/2024/10/decoding-europa-clipper/">https://destevez.net/2024/10/decoding-europa-clipper/</a> 2024-10-18T20:14:41Z https://yabu.me/nevent1qqswwfeagse8940ewxxce524whrnln6fdkkl2805a5c04dpjxakh29qzyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxwdcn8vw New blog post: Decoding Europa Clipper. A summary of my observation with the Allen Telescope Array after the launch, including a <span itemprop="mentions" itemscope itemtype="https://schema.org/Person"><a itemprop="url" href="/npub1xp6gmtlxtpsqz9j0mzm6zclwmdd09etgrh6mzd3enkams8rphf6sgvhh9m" class="bg-lavender dark:prose:text-neutral-50 dark:text-neutral-50 dark:bg-garnet px-1"><span>GNU Radio</span> (<span class="italic">npub1xp6…hh9m</span>)</a></span> decoder and the IQ recording. Some highlights: the modulation and coding is PCM/PM/NRZ r=1/6 Turbo with 1115 byte frames.<br/> <img src="https://files.mastodon.social/media_attachments/files/113/330/253/721/432/651/original/eae941ff3b91ef66.png"> <br/> 2024-10-18T20:14:06Z https://yabu.me/nevent1qqsgh6eazgwm8kvefqjcd9qy76wa3wszstz0xvha7n63puv72pzr3ygzyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxwyanjqy In reply to <a href='/nevent1qqsdsvqqvhx2w3933ygg4u2l79zlvn7sdzsyre99emkj55c37fksqnc35l897'>nevent1q…l897</a><br/>_________________________<br/><br/>I now managed to find an idle packet containing the complete message. The ending is a very nice touch.<br/> <img src="https://files.mastodon.social/media_attachments/files/113/313/177/160/561/443/original/29e63614a8992643.png"> <br/> 2024-10-15T19:51:19Z https://yabu.me/nevent1qqsdsvqqvhx2w3933ygg4u2l79zlvn7sdzsyre99emkj55c37fksqnczyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxwn0ws6a In reply to <a href='/nevent1qqsxqvu7j5d7au6t5hs54m9xjrpdfttlw2kchm6kuspya2lqhtedvmgegfhze'>nevent1q…fhze</a><br/>_________________________<br/><br/>The observation has just finished. Taking a quick look at the recording now. The same 12 kbaud r=1/6 Turbo 1115-byte frame modulation and coding has been maintained all the time. Idle Space Packets are &#34;signed&#34; by team members. Congratulations to them and the rest of the team!<br/> <img src="https://files.mastodon.social/media_attachments/files/113/307/683/309/186/013/original/f55aa6e6cebc8e6c.png"> <br/> 2024-10-14T20:34:03Z https://yabu.me/nevent1qqsxqvu7j5d7au6t5hs54m9xjrpdfttlw2kchm6kuspya2lqhtedvmgzyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxw0c9mqr In reply to <a href='/nevent1qqsg2npjhh8uyqj42t9hjxx06fq0kdtjc7qd5f3zwtc52xv3mf96syc5qwf54'>nevent1q…wf54</a><br/>_________________________<br/><br/>What looks like ranging tones has now appeared on the signal.<br/> <img src="https://files.mastodon.social/media_attachments/files/113/307/022/996/485/054/original/1088494ddf3cabe4.png"> <br/> 2024-10-14T17:46:14Z https://yabu.me/nevent1qqsg2npjhh8uyqj42t9hjxx06fq0kdtjc7qd5f3zwtc52xv3mf96syczyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxw0nf8dk We are tracking Europa Clipper with one 6 meter antenna at the Allen Telescope Array. Massively strong telemetry signal. Interestingly for such a low rate telemetry signal, there is no subcarrier.<br/> <img src="https://files.mastodon.social/media_attachments/files/113/307/004/041/167/516/original/a6312f8234444137.png"> <br/> 2024-10-14T17:41:28Z https://yabu.me/nevent1qqstleq75vukntchvcv285gu7gfy0hdr6uw8q8vaty97hgz4k6vkd4gzyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxwhxf0g7 In reply to <a href='/nevent1qqsy7f7zsqf4njge3wdvjh3y7790gupwxhvmnxcjgf9dlazfsuuzwuc5ut4j0'>nevent1q…t4j0</a><br/>_________________________<br/><br/>Remember that this is a dB scale. Some of the LOFAR measurements suggest that Starlink v2 can be up to 40 dB above the EMI limits for the automotive sector. Let me know if I made any mistakes with the calculations or if if you have more perspective on radiated EMI measurements. 2024-09-20T20:46:49Z https://yabu.me/nevent1qqsy7f7zsqf4njge3wdvjh3y7790gupwxhvmnxcjgf9dlazfsuuzwuczyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxwz4qdkc In reply to <a href='/nevent1qqsv5eanany3trgdskep3jpp22s437egpx44cx8rhq0zq47fsvkt92sxafgx4'>nevent1q…fgx4</a><br/>_________________________<br/><br/>So we have 78.2 dB μV/m at 3 m and 67.8 dB μV/m at 10 m (both in 120 kHz bandwidth). Comparing with typical radiated EMI limits, this seems like a lot. For instance <a href="https://ti.com/lit/wp/slyy142/slyy142.pdf">https://ti.com/lit/wp/slyy142/slyy142.pdf</a> gives 22 μV/m at 10 m with an average detector (LOFAR also measured average power).<br/> <img src="https://files.mastodon.social/media_attachments/files/113/171/836/368/677/513/original/f642ef12229eff77.png"> <br/> 2024-09-20T20:46:35Z https://yabu.me/nevent1qqsv5eanany3trgdskep3jpp22s437egpx44cx8rhq0zq47fsvkt92szyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxw7ja88p In reply to <a href='/nevent1qqsrau9fue45cpgv5rx2gk7fau4cu3escjwjrs4mqkxmxqcwvygn4ygavjyrx'>nevent1q…jyrx</a><br/>_________________________<br/><br/>The free space path loss at 1000 km (a typical slant range for a LEO satellite) and 60 MHz is -128 dB. So the transmitted EIRP is -17 dBm / 120 kHz. My background is in communications, and this sounds like a lot for an unwanted emission. Let&#39;s put it in perspective. EMI limits are measured in dB μV/m at 3 or 10 m distance. The conversion formula at 3 m is dB μV/m = EIRP(dBm) + 95.2 (<a href="https://yorkemc.com/wp-content/uploads/How_to_-_EIRP.pdf">https://yorkemc.com/wp-content/uploads/How_to_-_EIRP.pdf</a>). Going from 3 m to 10 m the field strength decreases by -10.4 dB = 20log10(3/10). 2024-09-20T20:45:42Z https://yabu.me/nevent1qqsrau9fue45cpgv5rx2gk7fau4cu3escjwjrs4mqkxmxqcwvygn4ygzyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxwz4tt6h In reply to <a href='/nevent1qqsxksmfhvjwq29znnqt2dzyta7dewj82wxrzt8a4d77aprnkv9vuxsneh6zj'>nevent1q…h6zj</a><br/>_________________________<br/><br/>We&#39;ll calculate things in 120 kHz bandwidth, because apparently that&#39;s the standard to measure EMI below 1 GHz (I know much more about communications than EMI, so do correct me if I make mistakes). We&#39;ll also normalize things for an isotropic 60 MHz antenna. An isotropic antenna has an aperture of λ²/(4π), which for 60 MHz gives 1.99 m². Thus the received power with such antenna in 120 kHz bandwidth is -145 dBm, which is obtained as -230+10*log10(1300 * 120e3 * 1.99). 2024-09-20T20:45:07Z https://yabu.me/nevent1qqsxksmfhvjwq29znnqt2dzyta7dewj82wxrzt8a4d77aprnkv9vuxszyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxwcdvc8k I&#39;m starting to read the paper about Starlink v2 VHF EMI received with LOFAR that recently made the rounds. Accompany me in doing some calculations to understand how strong this EMI actually is. I&#39;m comfortable with Jy, dBm and such, but use them in radically different contexts. So I need to convert to understand how strong something is. The paper mentions up to 1300 Jy between 56 and 66 MHz (let&#39;s call it 60 MHz). Recall that 1 Jy is -230 dBm per Hz of bandwidth and m² of receiver aperture.<br/> <img src="https://files.mastodon.social/media_attachments/files/113/171/828/172/102/448/original/61c2c394ea904e87.png"> <br/> 2024-09-20T20:44:36Z https://yabu.me/nevent1qqs053clzxlhhvlxlhtug674vc7c9ve7acz3ta7dmxzvs966x6gtn0gzyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxw52z328 New blog post: JUICE Earth flyby. I report on my failed attempt to receive the X-band telemetry with the Allen Telescope Array during the flyby, presumably because the spacecraft transmitter was off. <a href="https://destevez.net/2024/08/juice-earth-flyby/">https://destevez.net/2024/08/juice-earth-flyby/</a><br/> <img src="https://files.mastodon.social/media_attachments/files/113/004/443/631/481/700/original/41cfcc0cce2913ca.png"> <br/> 2024-08-22T07:16:45Z https://yabu.me/nevent1qqs0yacuh3950c47050nwpl9rnwhsfwe8ttjg7hxh6cfffy7hvpmzfgzyrjnyekk0k2nqzs3yvlehulzxyxp6pn7jhvy69qg0zvu85t4ffrxwsajtlz New blog post: Final update for the Galileo GST-UTC anomaly. In September-October 2023 I was covering an anomaly where the Galileo system time deviated much more than usual from UTC. Now that the event is long finished, I have updated my data analysis to show the full extent.<br/><br/>Read more: <a href="https://destevez.net/2024/08/final-update-for-the-galileo-gst-utc-anomaly/">https://destevez.net/2024/08/final-update-for-the-galileo-gst-utc-anomaly/</a><br/> <img src="https://files.mastodon.social/media_attachments/files/112/990/419/693/015/417/original/f4afb35e63994fe9.png"> <br/> 2024-08-19T19:50:39Z