New Reflective Half-Wave Plate Polarization Modulator with the team in Chile! Now installed on the second 90 GHz telescope 📡 This greatly increases the speed at which we measure the CMB linear polarization 🏎️ For more on the modulator: arxiv.org/abs/2407.08912.

Beautiful new reflective half-wave plate being made here. The copper sheen is about a kilometer's worth of 100 µm wire. Though admittedly with the handles and the color it looks like paella 🥘!

🚀 Science Fair day in San Pedro de Atacama, the main local community close to the telescopes 🇨🇱🫶 The CLASS site team Deniz and Jullianna created and hosted an interactive display about the telescopes and cosmology for students and other residents! 💫

!!! Congratulations to Rui Shi for successfully defending her PhD thesis: "Cosmology Large Angular Scale Surveyor: From Instrumentation to Beyond the Standard Model" !!!

🇧🇷 Brazilian CLASSmates, Jullianna and Deniz, receive an official "Motion of Applause" from the city council of their hometown for their work with CLASS and the recent results! 👏 www.instagram.com/reel/DLU5woH...

🐝🐝🐝 The CLASS site team has been busy! 🐝🐝🐝 Here is a video of them assembling the new receiver, which comes together as nested layers. When operating, all layers are under vacuum, and outer layers thermally shield colder layers underneath. The innermost is at 0.05 Kelvin!

To go along our recent result on reionization, the NSF Discovery Files podcast featured the CLASS project! #NSFfunded www.youtube.com/watch?v=uemq...

New detectors are installed on the new 90 GHz receiver at our Chile site! Go team!!

Em português. Mais nos comentários. www.correiobraziliense.com.br/ciencia-e-sa...

En español! Más en los comentarios! www.telemundo.com/shows/amp/rc...

The new array of 90 GHz detector modules is assembled in Chile. Ready to go into the new telescope! #NSFfunded

'People thought this couldn't be done': Scientists observe light of 'cosmic dawn' with a telescope on Earth for the first time ever www.livescience.com/space/astron...

Scientists detect 13 billion-year old signal from Cosmic Dawn using Earth-based telescopes indianexpress.com/article/tech...

Ground-based telescopes pierce cosmic dawn for first time www.courthousenews.com/ground-based...

Earth-based telescopes offer a fresh look at cosmic dawn | EurekAlert! www.eurekalert.org/news-release...

Earth Telescopes First to See Universe’s Cosmic Dawn scienceblog.com/earth-telesc...

💫 Here is a new JHU Hub article by Hannah Robbins to accompany the @aas.org‬ ApJ publication of our first optical depth measurement! 💫 #NSFfunded hub.jhu.edu/2025/06/11/t...

🎉 Just published in ApJ! Our paper on the first measurement of the reionization optical depth with ground based data! 🎉 We already have twice as much data in the can, so hopefully we'll have an updated result soon! #NSFfunded iopscience.iop.org/article/10.3...

The new 90 GHz telescope receiver has arrived at the CLASS site! 📡✨ The team pictured will now assemble and test the receiver before putting it on the telescope! #NSFfunded

Good morning!

New SPT-3G data release of the Euclid Deep Field-S taken in Nov-2024, with maps and source catalogs. In 57 deg^2, achieved depth of 4/4/13 uK-arcmin at 95/150/220 GHz, about 10x deeper than Planck, finding 114 dusty DSFGs and 217 galaxy clusters. @NSF arxiv.org/abs/2506.00298

International students are crucial team members in CLASS. They play a huge role in the success of CLASS and US science/tech. www.theguardian.com/us-news/2025...

New SPT-3G B-mode spectrum and r-constraint! "demonstrates a white noise level of 9.3 (6.7) µK-arcmin at ℓ∼500 for the 95GHz (150GHz) data, with a 1/ℓ noise knee at ℓ= 128 (182) with a statistical uncertainty on r of σ(r) = 0.067" arxiv.org/abs/2505.02827 @NSF @doescience

Update on the deployment of the second CLASS 90 GHz telescope: the telescope has passed through the Panama Canal on its way to Chile. And a team has started working on the polarization modulator already at the site.

🤓 Another interesting installment on reionization optical depth, this one including constraints on the ionization fraction from Ly-Alpha and on the duration of reionization from patchy kSZ. 💫 arxiv.org/abs/2505.15899

Bluesky at the observing site! 😎

✨Awesome progress!✨ Our high-school intern Jerome and mentor Carol Chan with Jerome's device to measure the heat 🌡️ of radiation entering the telescope receiver! Great job Jerome and Carol! 🚀 #NSFfunded!

Our latest big result! "A Measurement of the Largest-Scale CMB E-mode Polarization with CLASS" 🚀https://arxiv.org/abs/2501.11904

📡 Calling all astronomical instrumentation nerds! 🤓 Just posted today: here is the final word on our big 90 GHz telescope upgrade that nearly doubled our sensitivity in this important band! 🚀 arxiv.org/abs/2411.12705 #NSFFunded