What’s Up: September 2025 Skywatching Tips from NASA

Saturn’s spectacle, a Conjunction, and the Autumnal Equinox

Saturn shines throughout the month, a conjunction sparkles in the sky, and we welcome the autumnal equinox. 

Skywatching Highlights

• All of September: Saturn is visible
• Sept. 19: A conjunction between the Moon, Venus, and Regulus
• Sept. 21: Saturn is at opposition
• Sept. 22: The autumnal equinox

Transcript

What’s Up for September? Saturn puts on a spectacular show, a sunrise conjunction shines bright, and we ring in the autumnal equinox.

Saturn at Opposition

Saturn will be putting on an out-of-this-world performance this month. 

While Venus and Jupiter shine in the eastern morning sky, the ringed planet will be incredibly bright in the sky throughout September in the eastern evening sky and western early morning sky.

But why is Saturn the star of the show? Well, on September 21, Saturn will be at opposition, meaning Earth will find itself in between Saturn and the Sun, temporarily lined up. 

This also means that Saturn is at its closest and brightest all year! 

Saturn will be visible with just your eyes in the night sky, but with a small telescope, you might be able to see its rings!

Conjunction Trio

If you look to the east just before sunrise on September 19, you’ll see a trio of celestial objects in a magnificent conjunction. 

In the early pre-dawn hours, look east toward the waning, crescent Moon setting in the sky and you’ll notice something peculiar.
The Moon will be nestled up right next to both Venus and Regulus, one of the brightest stars in the night sky. 

The three are part of a conjunction, which simply means that they look close together in the sky (even if they’re actually far apart in space). 

To find this conjunction, just look to the Moon. 

And if you want some additional astronomical context, or want to specifically locate Regulus, this star lies within the constellation Leo, the lion. 

The Autumnal Equinox

On September 22, we mark the autumnal equinox or the official start of fall in the northern hemisphere. 

Astronomically, this is the time when the Sun finds itself exactly above the equator.

On this day, our planet isn’t tilted toward or away from the Sun, and both day and night are almost exactly 12 hours (with a few small exceptions). 

Moon Phases + Conclusion

Here are the phases of the Moon for September.

You can stay up to date on all of NASA’s missions exploring the solar system and beyond at science.nasa.gov.

I’m Chelsea Gohd from NASA’s Jet Propulsion Laboratory, and that’s What’s Up for this month.

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Circular Star Trails

On July 26, 2025, NASA astronaut Nichole Ayers took this long-exposure photograph – taken over 31 minutes from a window inside the International Space Station’s Kibo laboratory module – capturing the circular arcs of star trails.

In its third decade of continuous human presence, the space station has a far-reaching impact as a microgravity lab hosting technology, demonstrations, and scientific investigations from a range of fields. The research done on the orbiting laboratory will inform long-duration missions like Artemis and future human expeditions to Mars.

Image credit: NASA/Nichole Ayers

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Monika Luabeya

Advancing Single-Photon Sensing Image Sensors to Enable the Search for Life Beyond Earth

Advancing Single-Photon Sensing Image Sensors to Enable the Search for Life Beyond Earth

A NASA-sponsored team is advancing single-photon sensing Complementary Metal-Oxide-Semiconductor (CMOS) detector technology that will enable future NASA astrophysics space missions to search for life on other planets. As part of their detector maturation program, the team is characterizing sensors before, during, and after high-energy radiation exposure; developing novel readout modes to mitigate radiation-induced damage; and simulating a near-infrared CMOS pixel prototype capable of detecting individual photons.

Are we alone in the universe? This age-old question has inspired scientific exploration for centuries. If life on other planets evolves similarly to life on Earth, it can imprint its presence in atmospheric spectral features known asbiosignatures. They include absorption and emission lines in the spectrum produced by oxygen, carbon dioxide, methane, and other molecules that could indicate conditions which can support life. A future NASA astrophysics mission, the Habitable Worlds Observatory (HWO), will seek to find biosignatures in the ultraviolet, optical, and near-infrared (NIR) spectra of exoplanet atmospheres to look for evidence that life may exist elsewhere in the universe.

HWO will need highly sensitive detector technology to detect these faint biosignatures on distant exoplanets. The Single-Photon Sensing Complementary Metal-Oxide-Semiconductor (SPSCMOS) image sensor is a promising technology for this application. These silicon-based sensors can detect and resolve individual optical-wavelength photons using a low-capacitance, high-gain floating diffusion sense node. They operate effectively over a broad temperature range, including at room temperature. They have near-zero read noise, are tolerant to radiation, and generate very little unwanted signal—such as dark current. When cooled to 250 K, the dark current drops to just one electron every half-hour. If either the read noise or dark current is too high, the sensor will fail to detect the faint signals that biosignatures produce.

A research team at the Rochester Institute of Technology (RIT) Center for Detectors (CfD) is accelerating the readiness of these SPSCMOS sensors for use in space missions through detector technology maturation programs funded by NASA’s Strategic Astrophysics Technology and Early Stage Innovations solicitations. These development programs include several key goals:

• Characterize critical detector performance metrics like dark current, quantum efficiency, and read noise before, during, and after exposure to high-energy radiation
• Develop new readout modes for these sensors to mitigate effects from short-term and long-term radiation damage
• Design a new NIR version of the sensor using Technology Computer-Aided Design (TCAD) software

SPSCMOS sensors operate similarly to traditional CMOS image sensors but are optimized to detect individual photons—an essential capability for ultra-sensitive space-based observations, such as measuring the gases in the atmospheres of exoplanets. Incoming photons enter the sensor and generate free charges (electrons) in the sensor material. These charges collect in a pixel’s storage well and eventually transfer to a low-capacitance component called the floating diffusion (FD) sense node where each free charge causes a large and resolved voltage shift. This voltage shift is then digitized to read the signal.

Experiments that measure sensor performance in a space relevant environment use a vacuum Dewar and a thermally-controlled mount to allow precise tuning of the sensors temperature. The Dewar enables testing at conditions that match the expected thermal environment of the HWO instrument, and can even cool the sensor and its on-chip circuits to temperatures colder than any prior testing reported for this detector family. These tests are critical for revealing performance limitations with respect to detector metrics like dark current, quantum efficiency, and read noise. As temperatures change, the electrical properties of on-chip circuits can also change, which affects the read out of charge in a pixel.

The radiation-rich environment for HWO will cause temporary and permanent effects in the sensor. These effects can corrupt the signal measured in a pixel, interrupt sensor clocking and digital logic, and can cause cumulative damage that gradually degrades sensor performance. To mitigate the loss of detector sensitivity throughout a mission lifetime, the RIT team is developing new readout modes that are not available in commercial CMOS sensors. These custom modes sample the signal over time (a “ramp” acquisition) to enable the detection and removal of cosmic ray artifacts. In one mode, when the system identifies an artifact, it segments the signal ramp and selectively averages the segments to reconstruct the original signal—preserving scientific data that would otherwise be lost. In addition, a real-time data acquisition system monitors the detector’s power consumption, which may change from the accumulation of damage throughout a mission. The acquisition system records these shifts and communicates with the detector electronics to adjust voltages and maintain nominal operation. These radiation damage mitigation strategies will be evaluated during a number of test programs at ground-based radiation facilities. The tests will help identify unique failure mechanisms that impact SPSCMOS technology when it is exposed to radiation equivalent to the dose expected for HWO.

While existing SPSCMOS sensors are limited to detecting visible light due to their silicon-based design, the RIT team is developing the world’s first NIR single-photon photodiode based on the architecture used in the optical sensors. The photodiode design starts as a simulation in TCAD software to model the optical and electrical properties of the low-capacitance CMOS architecture. The model simulates light-sensitive circuits using both silicon and Mercury Cadmium Telluride (HgCdTe or MCT) material to determine how well the pixel would measure photo-generated charge if a semiconductor foundry physically fabricated it. It has 2D and 3D device structures that convert light into electrical charge, and circuits to control charge transfer and signal readout with virtual probes that can measure current flow and electric potential. These simulations help to evaluate the key mechanisms like the conversion of light into electrons, storing and transferring the electrons, and the output voltage of the photodiode sampling circuit.

In addition to laboratory testing, the project includes performance evaluations at a ground-based telescope. These tests allow the sensor to observe astronomical targets that cannot be fully replicated in lab. Star fields and diffuse nebulae challenge the detector’s full signal chain under real sky backgrounds with faint flux levels, field-dependent aberrations, and varying seeing conditions. These observations help identify performance limitations that may not be apparent in controlled laboratory measurements.

In January 2025, a team of researchers led by PhD student Edwin Alexani used an SPSCMOS-based camera at the C.E.K. Mees Observatory in Ontario County, New York. They observed star cluster M36 to evaluate the sensor’s photometric precision, and the Bubble Nebula in a narrow-band H-alpha filter. The measured dark current and read noise were consistent with laboratory results.

The team observed photometric reference stars to estimate the quantum efficiency (QE) or the ability for the detector to convert photons into signal. The calculated QE agreed with laboratory measurements, despite differences in calibration methods.

The team also observed the satellite STARLINK-32727 as it passed through the telescope’s field of view and measured negligible persistent charge—residual signal that can remain in detector pixels after exposure to a bright source. Although the satellite briefly produced a bright streak across several pixels due to reflected sunlight, the average latent charge in affected pixels was only 0.03 e^–/pix – well below both the sky-background and sensor’s read noise.

As NASA advances and matures the HWO mission, SPSCMOS technology promises to be a game-changer for exoplanet and general astrophysics research. These sensors will enhance our ability to detect and analyze distant worlds, bringing us one step closer to answering one of humanity’s most profound questions: are we alone?

For additional details, see the entry for this project on NASA TechPort.

Project Lead(s): Dr. Donald F. Figer, Future Photon Initiative and Center for Detectors, Rochester Institute of Technology (RIT), supported by engineer Justin Gallagher and a team of students.

Sponsoring Organization(s): NASA Astrophysics Division, Strategic Astrophysics Technology (SAT) Program and NASA Space Technology Mission Directorate (STMD), Early Stage Innovations (ESI) Program

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Tech From NASA’s Hurricane-hunting TROPICS Flies on Commercial Satellites

NASA science and American industry have worked hand-in-hand for more than 60 years, transforming novel technologies created with NASA research into commercial products like cochlear implants, memory-foam mattresses, and more. Now, a NASA-funded device for probing the interior of storm systems has been made a key component of commercial weather satellites.

The novel atmospheric sounder was originally developed for NASA’s TROPICS (short for Time-Resolved Observations of Precipitation structure and storm Intensity with a Constellation of SmallSats), which launched in 2023. Boston-based weather technology company Tomorrow.io integrated the same instrument design into some of its satellites.

Atmospheric sounders allow researchers to gather data describing humidity, temperature, and wind speed — important factors for weather forecasting and atmospheric analysis. From low-Earth orbit, these devices help make air travel safer, shipping more efficient, and severe weather warnings more reliable.

Novel tools for Observing Storm Systems

In the early 2000s, meteorologists and atmospheric chemists were eager to find a new science tool that could peer deep inside storm systems and do so multiple times a day. At the same time, CubeSat constellations (groupings of satellites each no larger than a shoebox) were emerging as promising, low-cost platforms for increasing the frequency with which individual sensors could pass over fast-changing storms, which improves the accuracy of weather models.

The challenge was to create an instrument small enough to fit aboard a satellite the size of a toaster, yet powerful enough to observe the innermost mechanisms of storm development. Preparing these technologies required years of careful development that was primarily supported by NASA’s Earth Science Division.

William Blackwell and his team at MIT Lincoln Laboratory in Cambridge, Massachusetts, accepted this challenge and set out to miniaturize vital components of atmospheric sounders. “These were instruments the size of a washing machine, flying on platforms the size of a school bus,” said Blackwell, the principal investigator for TROPICS. “How in the world could we shrink them down to the size of a coffee mug?”

With a 2010 award from NASA’s Earth Science Technology Office (ESTO), Blackwell’s team created an ultra-compact microwave receiver, a component that can sense the microwave radiation within the interior of storms.

The Lincoln Lab receiver weighed about a pound and took up less space than a hockey puck. This innovation paved the way for a complete atmospheric sounder instrument small enough to fly aboard a CubeSat. “The hardest part was figuring out how to make a compact back-end to this radiometer,” Blackwell said. “So without ESTO, this would not have happened. That initial grant was critical.”

In 2023, that atmospheric sounder was sent into space aboard four TROPICS CubeSats, which have been collecting torrents of data on the interior of severe storms around the world.

Transition to Industry

By the time TROPICS launched, Tomorrow.io developers knew they wanted Blackwell’s microwave receiver technology aboard their own fleet of commercial weather satellites. “We looked at two or three different options, and TROPICS was the most capable instrument of those we looked at,” said Joe Munchak, a senior atmospheric data scientist at Tomorrow.io.

In 2022, the company worked with Blackwell to adapt his team’s design into a CubeSat platform about twice the size of the one used for TROPICS. A bigger platform, Blackwell explained, meant they could bolster the sensor’s capabilities.

“When we first started conceptualizing this, the 3-unit CubeSat was the only game in town. Now we’re using a 6-unit CubeSat, so we have room for onboard calibration,” which improves the accuracy and reliability of gathered data, Blackwell said.

Tomorrow.io’s first atmospheric sounders, Tomorrow-S1 and Tomorrow-S2, launched in 2024. By the end of 2025, the company plans to have a full constellation of atmospheric sounders in orbit. The company also has two radar instruments that were launched in 2023 and were influenced by NASA’s RainCube instrument — the first CubeSat equipped with an active precipitation radar.

More CubeSats leads to more accurate weather data because there are more opportunities each day — revisits — to collect data. “With a fleet size of 18, we can easily get our revisit rate down to under an hour, maybe even 40 to 45 minutes in most places. It has a huge impact on short-term forecasts,” Munchak said.

Having access to an atmospheric sounder that had already flown in space and had more than 10 years of testing was extremely useful as Tomorrow.io planned its fleet. “It would not have been possible to do this nearly as quickly or nearly as affordably had NASA not paved the way,” said Jennifer Splaingard, Tomorrow.io’s senior vice president for space and sensors.

A Cycle of Innovation

The relationship between NASA and industry is symbiotic. NASA and its grantees can drive innovation and test new tools, equipping American businesses with novel technologies they may otherwise be unable to develop on their own. In exchange, NASA gains access to low-cost data sets that can supplement information gathered through its larger science missions.

Tomorrow.io was among eight companies selected by NASA’s Commercial SmallSat Data Acquisition (CSDA) program in September 2024 to equip NASA with data that will help improve weather forecasting models. “It really is a success story of technology transfer. It’s that sweet spot, where the government partners with tech companies to really take an idea, a proven concept, and run with it,” Splaingard said.

By Gage Taylor

NASA’s Goddard Space Flight Center, Greenbelt, Md.

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Katy Mersmann