Cees Bassa

It's cleared up in Sydney and I can see the shadow creeping across the Moon! 🥳🌚🔭

💥Greater (partial) success for #amateurradio and #amsat satellite operators in dispute with AST Spacemobile over commercial use of the 430-440 MHz amateur radio band for TT&C! 💥 In its reference Attachment to the recent grant, dated August 29, 2025, the FCC imposes clear limits ⬇️

NOAA-15 was decommissioned today at 15:26 UTC, with its AVHRR/3 Instrument still in better state than the last 2 remaining on MetOp-B & C.

It wouldn't be so disappointing if this wasn't done for the wrong reasons... Makes you wonder what happened to NOAA.

Slide modelling the orbits of satellites and how often they enter a telescope’s field of view.

Slide 2 about modelling the orbits of satellites and how often they enter a telescope’s field of view.

#skao2025 Federico Di Vruno on impact of satellites on #RadioAstronomy from intended emissions (strong enough to saturate receivers) & unintended electromagnetic radiation (originating from on satellite electronics). In future 🛰️ constellations could impact 25% of our observing time! 🔭📡🧪

Near-future rocket launches could slow ozone recovery npj Climate and Atmospheric Science - Near-future rocket launches could slow ozone recovery

New paper day! In 'Near-future rocket launches could slow ozone recovery', we show that scaling up use of launch vehicles 🚀 has a point where the healing of the ozone layer is affected 🧪🛰️
Open access, free to read & share

Glad to hear you found the software useful!

Here, strf was used by the UVSQSat-NG team :
- at the beginning of the mission to optimize the preliminary TLEs so that the university could establish the most reliable communication possible,
- for monitoring purposes since refined TLEs have become available...

Thank you for the great work!

Unfortunately the surface of the Moon is also quite hard.

We lost HAKUTO-R M2 signal suddenly

We have lost signal of Hakuto-R M2 Resilience! We saw the signal and its Lunar reflection close to each other before LOS, indicating that it was very close to the surface when the signal disappeared. Space is hard!

Livestream CAMRAS Radiotelescoop YouTube video by CAMRAS Radiotelescoop

We are now tracking the landing attempt of #Hakuto-R Mission 2 #Resilience. Check our livestream at www.youtube.com/live/C7-MQ2U...

It looks like not just Satdump was used as the software for this project! I recognize the spectrogram plots. I hope STRF has been useful as well.

On the occasion of the @unesco.org International Day of Light, we created a 'light painting' using the Dwingeloo Telescope by mounting a light bulb at the focus for half an hour. #lightday2025 @idlofficial.bsky.social

And Magritte fans 😀

Black smoke from the papal chimney.

Two days too late and perhaps only funny for those speaking Dutch. (H/T Gemma Janssen.)

Maybe the upper stage failure ended up tumbling the spacecraft fast enough to break it up?

Following up on @marcolangbroek.bsky.social 's post on the upcoming Venera capsule reentry, I've done a writeup describing my own analysis of this object, which I first got interested in a quarter century ago!
planet4589.org/space/debris...

Thanks for the write up. One thing I've not seen discussed is why the descent stage would've separated in Earth orbit. I assume the whole probe would've needed a cruise stage for the trip to Venus of which it would have to separate. Have you come across any information that might explain that?

CHIME All-sky Multiday Pulsar Stacking Search (CHAMPSS): System Overview and First Discoveries We describe the CHIME All-sky Multiday Pulsar Stacking Search (CHAMPSS) project. This novel radio pulsar survey revisits the full Northern Sky daily, offering unprecedented opportunity to detect highl...

Time for some science again... We are finding new pulsars with CHIME by stacking data over multiple days to boost sensitivity. As always, a huge effort by multiple postdocs, students and programmers.

arxiv.org/abs/2504.16293

A plot with the same title as before: Frequency difference between Bochum and Dwingeloo (with Doppler for Mare Crisium subtracted). The curve is now different. It is a noisy ramp that increases from -1.75 Hz to 0.75 Hz.

After fixing this mistake, the frequency difference is on the order of 1 Hz. This is about 0.7 ppb, so it is within the accuracy that we could expect for the GPSDO at Bochum. So mystery solved!

Great work! This is why we put our IQ on the web :)
One remark on why Dwingeloo is less sensitive: we have a relay in front of the first LNA, because Dwingeloo also transmits in experiments like this one. Apart from that, we may also need a better LNA.

My solution for this has been to use SPKCPO to get the state vector of the center of Venus, and then use SXFORM and MXVG to convert surface positions on Venus to offset positions and velocities in the observer frame. This works but the delay/doppler needs to be computed separately for each position.

And thanks for the discussion of the SPICE functions you used. This is something I struggled with as well as it appears there is no SPICE function that'll compute the state vector between a surface position on a target body and a surface position on an observing body.

A plot of the power spectral density of the signal as received in Stockert and Dwingeloo. The plot is normalized so that the noise has mean zero and standard deviation one, so the detection values in sigmas can be read directly. There is a continuous trace showing the measurement of the PFB spectrum analyzer with 0.5 Hz bins, and a dashed trace that is a moving average of 5 of these bins.

A plot of the power spectral density of the maximum ratio combining of the signals at Stockert and Dwingeloo. The Doppler spread model is also shown for comparison. The model predicts a slightly larger Doppler spread than what observed in practice. As in the previous plot, the spectrum is normalize so that noise has mean zero and standard deviation one, and both the spectrum in 0.5 Hz bins and a moving average of 5 bins are shown.

The signal can be detected both in the Dwingeloo and Stockert 25 m radio telescopes, but the performance of Dwingeloo is poorer. The observed Doppler spread is on the order of ±0.75 Hz, which is a bit less than the spread model I made.

Read more: destevez.net/2025/04/anal...

Original paper is at ui.adsabs.harvard.edu/abs/1967AJ..... and our simulations could reproduce the observed curves for all their observing dates. The backscatter power relation we used is from Evans & Hagfors (Radar Astronomy, p306).

Thanks for the independent analysis! The doppler spread curve is one that we had looked at to estimate the loss in the link budget, which was about 3dB in 1Hz. Using Arecibo radar measurements of Venus from 1964 we could reproduce the delay-doppler curve from Dyce et al. 1967 (red points).

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 @radiotelescoop.bsky.social, Astropeiler Stockert, the Deep Space Exploration Society, and Open Research Institute. 🧵

Oh dear ... "Mr Eclipse" Fred Espenak just wrote this on a mailing list and on facebook.com/fred.espenak.... The eclipse scene has lost so many of its greatest in the last three years, Jay Pasachof, Serge Kouchmy, Glenn Schneider, and now its towering figure will leave us. :-(