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1. UNDERSTANDING THE IMPACT OF SATELLITES ON RADIO ASTRONOMY OBSERVATIONS

   Peel, M; Eggl, S; Rawls, ML; Qui, H; Clements, DL (May 2025, European Space Agency Space Debris Office)

   Lemmens, S; Flohrer, T; Schmitz, F (Ed.)

   Radio telescopes observe extremely faint emission from astronomical objects, ranging from compact sources to large scale structures that can be seen across the whole sky. Satellites actively transmit at radio frequencies (particularly at 10±20 GHz, but usage of increasing broader frequency ranges are already planned for the future by satellite operators), and can appear as bright as the Sun in radio astronomy observations. Remote locations have historically enabled telescopes to avoid most interference, however this is no longer the case with dramatically increasing numbers of satellites that transmit everywhere on Earth. Even more remote locations such as the far side of the Moon may provide new radio astronomy observation opportunities, but only if they are protected from satellite transmissions. Improving our understanding of satellite transmissions on radio telescopes across the whole spectrum and beyond is urgently needed to overcome this new observational challenge, as part of ensuring the future access to dark and quiet skies. In this contribution we summarise the current status of observations of active satellites at radio frequencies, the implications for future astronomical observations, and the longer-term consequences of an increasing number of active satellites. This will include frequencies where satellites actively transmit, where they unintentionally also transmit, and considerations about thermal emission and other unintended emissions. This work is ongoing through the IAU CPS. 

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2. The Renovated Thacher Observatory and First Science Results

   https://doi.org/10.1088/1538-3873/ac5aca  

   Swift, Jonathan J.; Andersen, Karina; Arculli, Toby; Browning, Oakley; Ding, Jeffrey; Edwards, Nick; Fanning, Tomás; Geyer, John; Huber, Grace; Jin-Ngo, Dylan; et al (March 2022, Publications of the Astronomical Society of the Pacific)

   Abstract Located on the campus of the Thacher School in Southern California, the Thacher Observatory has a legacy of astronomy research and education that dates back to the late 1950s. In 2016, the observatory was fully renovated with upgrades including a new 0.7 m telescope, a research grade camera, and a slit dome with full automation capabilities. The low-elevation site is bordered by the Los Padres National Forest and therefore affords dark to very dark skies allowing for accurate and precise photometric observations. We present a characterization of the site including sky brightness, weather, and seeing, and we demonstrate the on-sky performance of the facility. Our primary research programs are based around our multi-band photometric capabilities and include photometric monitoring of variable sources, a nearby supernova search and followup program, a quick response transient followup effort, and exoplanet and eclipsing binary light curves. Select results from these programs are included in this work which highlight the broad range of science available to an automated observatory with a moderately sized telescope. 

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3. Observing the mid-latitude aurora

   https://doi.org/10.1117/12.2531275  

   Shaw, Joseph A.; Shaw, Joseph A.; Creath, Katherine; Lakshminarayanan, Vasudevan (August 2019, Proc. SPIE 11099)

   The aurora is a beautiful night sky optical phenomenon that is readily seen at high-latitude locations, but with more effort can also be seen and enjoyed at mid-latitude locations. Guidelines for when and where to look are presented, along with a rich array of photographic examples of mid-latitude auroras exhibiting all the usual range of green, red, and purple colors. 

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4. Phosphoketolase and KDPG aldolase metabolisms modulate photosynthetic carbon yield in cyanobacteria

   https://doi.org/10.1093/plcell/koae291  

   Xie, Ningdong; Sharma, Chetna; Rusche, Katherine; Wang, Xin (December 2024, The Plant Cell)

   Abstract Cyanobacteria contribute to roughly a quarter of global net carbon fixation. During diel light/dark growth, dark respiration substantially lowers the overall photosynthetic carbon yield in cyanobacteria and other phototrophs. How respiratory pathways participate in carbon resource allocation at night to optimize dark survival and support daytime photosynthesis remains unclear. Here, using the cyanobacterium Synechococcus elongatus PCC 7942, we show that phosphoketolase integrates into a respiratory network in the dark to best allocate carbon resources for amino acid biosynthesis and to prepare for photosynthesis reinitiation upon photoinduction. Moreover, we show that the respiratory Entner–Doudoroff pathway in S. elongatus is incomplete, with its key enzyme 2-keto-3-deoxy-6-phosphogluconate aldolase exhibiting alternative oxaloacetate decarboxylation activity that modulates daytime photosynthesis. This activity allows for the bypassing of the tricarboxylic acid cycle when ATP and NADPH consumption for biosynthesis is excessive and imbalanced relative to their production by the light reactions, thereby preventing relative NADPH accumulation and ensuring optimal photosynthetic carbon yield. Optimizing these metabolic processes offers opportunities to enhance photosynthetic carbon yield in cyanobacteria and other photosynthetic organisms under diel light/dark cycles. 

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5. Multiomics resolution of molecular events during a day in the life of Chlamydomonas

   https://doi.org/10.1073/pnas.1815238116  

   Strenkert, Daniela; Schmollinger, Stefan; Gallaher, Sean D.; Salomé, Patrice A.; Purvine, Samuel O.; Nicora, Carrie D.; Mettler-Altmann, Tabea; Soubeyrand, Eric; Weber, Andreas P. M.; Lipton, Mary S.; et al (February 2019, Proceedings of the National Academy of Sciences)

   The unicellular green algaChlamydomonas reinhardtiidisplays metabolic flexibility in response to a changing environment. We analyzed expression patterns of its three genomes in cells grown under light–dark cycles. Nearly 85% of transcribed genes show differential expression, with different sets of transcripts being up-regulated over the course of the day to coordinate cellular growth before undergoing cell division. Parallel measurements of select metabolites and pigments, physiological parameters, and a subset of proteins allow us to infer metabolic events and to evaluate the impact of the transcriptome on the proteome. Among the findings are the observations thatChlamydomonasexhibits lower respiratory activity at night compared with the day; multiple fermentation pathways, some oxygen-sensitive, are expressed at night in aerated cultures; we propose that the ferredoxin, FDX9, is potentially the electron donor to hydrogenases. The light stress-responsive genesPSBS,LHCSR1, andLHCSR3show an acute response to lights-on at dawn under abrupt dark-to-light transitions, whileLHCSR3genes also exhibit a later, second burst in expression in the middle of the day dependent on light intensity. Each response to light (acute and sustained) can be selectively activated under specific conditions. Our expression dataset, complemented with coexpression networks and metabolite profiling, should constitute an excellent resource for the algal and plant communities. 

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