That window matters because Earth’s radiation budget is arguably the single most important number in climate science. It describes the balance between the solar energy Earth absorbs and the thermal energy it radiates back to space. When the planet absorbs more than it emits, global mean surface temperature rises; when the reverse occurs, it falls. Both the Intergovernmental Panel on Climate Change and the most recent Earth science Decadal Survey designate these observations as essential for determining the current energy imbalance and predicting future climate, and the Global Climate Observing System classifies the radiation budget as an Essential Climate Variable. Because the climate system responds over decadal to centennial timescales, only continuous, accurate monitoring from space can reveal the mechanisms driving climate shifts and inform mitigation strategies.

The gold standard for such monitoring is the Clouds and the Earth’s Radiant Energy System, or CERES, a suite of scanning broadband radiometers that has maintained the longest continuous record of Earth’s radiative energy, stretching from 2000 to the present. Six CERES instruments flying on four satellites, Terra, Aqua, Suomi-NPP, and NOAA-20, have collectively delivered more than 26 years of measurements of reflected solar and emitted longwave radiation. Yet the record faces a looming threat. The CERES instruments on Terra and Aqua are scheduled to end science operations in 2027, and S-NPP potentially in 2026. NASA’s first Earth Venture Continuity mission, Libera, is set to launch in late 2027 with a five-year prime mission, but no missions are planned beyond it. According to a recent analysis cited in the study, the probability of a gap in the radiation budget record reaches 33 percent by 2028 and climbs to 60 percent by 2035, even assuming Libera remains operational. Worse, bridging a gap produces errors roughly four times larger than those arising when successive missions overlap.

Against that backdrop, the CTIM team saw an opportunity. Because the CubeSat was designed for solar irradiance, its electrical substitution radiometers, equipped with vertically aligned carbon nanotube absorbers that absorb more than 99.9 percent of incident radiation from the ultraviolet through the infrared, were calibrated in irradiance rather than radiance. During orbital eclipse, the spacecraft was pointed at Earth’s nadir, collecting calibrated irradiance measurements that the team converted to mean radiance using the instrument’s precisely characterized angular response, which reached zero at 23 degrees off-axis. At a median orbital altitude of 453 kilometers, that translated into a footprint roughly 484 kilometers in diameter, enormous compared with the 20-kilometer nadir footprints of the CERES scanners, but well suited to averaging broad scenes of outgoing thermal emission.

To find out whether these opportunistic measurements could stand shoulder to shoulder with the established record, the researchers compared CTIM’s nighttime longwave radiances with coincident observations from CERES instruments aboard Terra, Aqua, and NOAA-20. They built a four-step matching algorithm that selected CERES footprints within 242 kilometers of each CTIM footprint centroid and within 20 minutes of each CTIM observation, restricted to viewing zenith angles of 20 degrees or less to match CTIM’s near-nadir geometry, and required at least 400 CERES samples per match. The procedure yielded 541 matches containing 261,010 individual CERES footprints. Supplemental CERES observations filled gaps within each CTIM footprint, and the team weighted every CERES radiance by the CTIM spatial response function and by the viewing-angle-dependent growth of the CERES footprint area.

One subtlety demanded extra care. When a scanning radiometer views Earth at oblique angles, the observed radiance typically decreases because radiation travels a longer path through the cooler upper atmosphere, an effect known as limb darkening. Since CERES footprints extended up to nearly 30 degrees off nadir within the CTIM footprint, the team ran 700 radiative transfer simulations with the MODTRAN code, varying viewing angle, surface emissivity, surface temperature, and atmospheric profile across tropical, mid-latitude summer, and mid-latitude winter conditions. The resulting lookup tables provided limb-darkening adjustment factors that were applied to the 17.6 percent of CERES footprints meeting a strict clear-sky criterion of at least 95 percent clear fraction, ensuring that off-nadir radiances were consistent with CTIM’s nadir-viewing geometry.

The verdict was striking. Across all 541 matches, the mean relative difference between CTIM and CERES longwave radiances was −1.19 percent, with a bootstrapped 95 percent confidence interval of ±0.35 percent and a standard deviation of 4.16 percent. A linear regression produced a coefficient of determination of 0.948 and a root mean square error of 3.02 watts per square meter per steradian, indicating a strong relationship between the two instruments. Individually, Terra yielded a relative difference of −1.18 ± 0.45 percent over 238 matches, Aqua −1.21 ± 1.08 percent over 109 matches, and NOAA-20 −1.18 ± 0.53 percent over 194 matches, all well within the respective instrument uncertainties. CTIM’s own radiance uncertainty budget, dominated by solid-angle uncertainty, totaled 1.65 to 1.80 percent, while CERES longwave calibration uncertainty is about 0.75 percent. The agreement demonstrates that a solar instrument never designed for Earth observation can nonetheless deliver scientifically credible measurements of the planet’s thermal emission.

The residual spread in the comparison told its own story. When the team stratified scenes by cloud cover, clear-sky matches showed a standard deviation of only 1.17 percent, compared with 4.26 percent for cloudy scenes, and the largest spreads of all appeared in the tropical latitude bins straddling the equator, where persistent deep convective clouds of the inter-tropical convergence zone create highly heterogeneous scenes. Because the CERES scanners view clouds along oblique paths while CTIM looks straight down, the two instruments sample cloud layers along meaningfully different path lengths, introducing sensitivity to cloud optical depth and vertical structure. Even CTIM’s gridded global map of 15 months of nighttime observations reproduced familiar features of the longwave radiation field, including the characteristic minimum over the tropics where high, cold cloud tops suppress thermal emission, qualitatively mirroring 17 years of CERES climatology.

The implications reach well beyond a single technology demonstration. CubeSats offer low launch costs, flexible deployment, and redundancy that large flagship missions cannot match; three independent CubeSats with a three-year survival probability of 63 percent each collectively achieve a 95 percent success probability. A growing family of small-satellite missions, including RAVAN, NASA’s polar-orbiting PREFIRE pair, the French Uvsq-Sat constellation and its successor Uvsq-Sat NG, and the proposed BABAR-ERI concept, is already charting the path. The CTIM results suggest a particularly elegant strategy: future total solar irradiance instruments could be intentionally designed with Earth-viewing capability built in, allowing a single low-cost platform to monitor both the Sun and the planet. With an optical system purpose-built for Earth’s wider angular spread of outgoing radiation, radiance uncertainties could shrink toward the 0.02 percent level achieved for solar measurements. Challenges remain, including long-term radiometric stability, absolute Earth-viewing calibration, and cloud anisotropy corrections, but the study makes a compelling case that fleets of small, cheap, rapidly deployable radiometers could buffer the radiation budget record against the gaps that currently threaten to open after 2027, protecting the multidecadal climate data record on which our understanding of a warming planet depends.

Subject of Research: CubeSat-based continuity observations of Earth's radiation budget from space

Article Title: From opportunity to continuity: a CubeSat implementation to enhance Earth's radiation budget observations from space

Article References: A. Hawkins, M., Watwood, M., van den Heever, M., Pilewskie, P., & Harber, D. (2026). From opportunity to continuity: a CubeSat implementation to enhance Earth's radiation budget observations from space. Atmospheric Measurement Techniques, 19(19), 6229-6250. https://doi.org/10.5194/amt-19-6229-2026

Image Credits: AI Generated

DOI: 10.5194/amt-19-6229-2026

Keywords: Earth radiation budget, CubeSat, CTIM, CERES, total solar irradiance, longwave radiation, climate data record, Libera, remote sensing, satellite calibration, limb darkening, NASA InVEST

The physics behind these sails is deceptively simple but demanding in practice. Photons carry momentum even though they have no mass, and when sunlight reflects off a thin reflective membrane, the momentum transfer exerts a small but continuous force. Unlike chemical rockets that burn out after minutes, a light sail accelerates for as long as it faces a light source, which is why the concept has long been championed for ambitious missions such as Breakthrough Starshot, which envisions laser-driven sails carrying tiny probes to nearby star systems. The challenge has always been engineering: a sail must be extraordinarily light, fold into a tiny launch volume, and deploy reliably in the unforgiving environment of space. Cornell’s approach attacks all three constraints at once by folding the sail origami-style inside a CubeSat and pairing it with ChipSat electronics that weigh a fraction of a conventional satellite bus.

Alpha CubeSat, a 1U CubeSat funded through NASA’s CubeSat Launch Initiative, deployed its light sail in low Earth orbit. The mission’s most striking early result came through the TinyGS network, a distributed array of amateur ground stations around the world, which established contact with the ChipSat riding on the sail. According to Joshua Umansky-Castro, the mission lead and a recent graduate of Cornell’s Aerospace Engineering Ph.D. program, this was the first time a spacecraft this small transmitted complete data packets from orbit to ground. He described the achievement as a huge milestone that advances the state of the art for the ChipSat platform. The sail itself met a quick end, as atmospheric drag at low altitude rapidly decelerated the ultralight structure, but the communications demonstration had already been secured.

Until its deorbit in May 2026, the Alpha CubeSat confirmed successful sail deployment and carried out a remarkable series of secondary technology demonstrations. The spacecraft performed spin stabilization using only magnetorquers, coils that interact with Earth’s magnetic field to control attitude without moving parts or propellant. Its avionics were built entirely from commercial off-the-shelf components, including the first-ever flight of a RockBLOCK Iridium modem, which allows a small satellite to communicate through the Iridium satellite constellation. The chassis was fully 3D-printed, and the mission even carried the first holographic-image message plaques sent to space, part of an effort to embed durable messages on light sails that might one day travel to other stars.

The companion experiment, Sailing to the Stars, took a different approach to the same problem by testing sail deployment inside the microgravity environment of the space station itself. Funded by the ISS National Laboratory in collaboration with Rhodium Scientific, the experiment deployed six of the light sails and captured critical video footage and inertial measurement unit data. This combination gives the student engineers a direct view of how the sails unfurl and how the deployment dynamics behave when gravity does not mask subtle oscillations, snags, or asymmetric release. Understanding these kinematics on the station is far cheaper and safer than discovering them during an orbital deployment that cannot be repeated or repaired.

A particularly inventive aspect of the Sailing to the Stars experiment was the hardware itself. Two different CubeSat-scale deployer designs were tested, both built entirely from 3D-printed modular components the team describes as CubeSat-LEGO. The deployers were spin-stabilized using reaction wheels salvaged from laptop hard disk drives, and they were commanded using ordinary TV remote controls. This deliberate use of consumer hardware reflects a philosophy of radical cost reduction: if a deployment mechanism can be validated with parts costing a few dollars, the barrier to flying many more sail missions drops dramatically. By comparing video and IMU data from both designs, the team assessed which release mechanism produced more stable kinematics, and those insights now feed directly into the design of future missions.

The human story behind the hardware is as notable as the technology. The original concept for Alpha was proposed by a high school student through the Museum of Science Fiction’s International CubeSat Design Competition, and since 2016 more than 150 students have contributed to the spacecraft projects. Over half of those participants have gone on to intern or work in the aerospace industry after graduation. Verena Padres, a member of the class of 2026 who managed the Sailing to the Stars project, said that working on something that would fly in space was her dream going into college, and that she was grateful not only for hands-on spacecraft engineering experience but for the chance to lead the team from mission concept through launch.

What makes the ChipSat-sail combination significant for the broader field is the mass budget it opens up. Traditional solar sails require booms, deployment mechanisms, avionics, and power systems that can add kilograms, and that mass directly reduces the acceleration the sail can achieve for a given area. By making the sail itself the structural carrier and letting a gram-scale ChipSat handle communications and steering, the Cornell design shrinks the total system mass toward the regime where photon pressure becomes genuinely useful for propulsion. The team’s stated roadmap builds on this: future ChipSat-sail launches are planned to demonstrate steering, orbit-raising, and laser propulsion, with longer-term ambitions extending to solar system exploration missions targeting the moon, Mars, and beyond.

The ultimate destination, as the team emphasizes, is interstellar space. Initiatives such as Breakthrough Starshot have argued that sails riding on powerful laser beams could one day propel tiny spacecraft to a significant fraction of the speed of light, reaching nearby star systems within a human lifetime in the search for life beyond Earth. Demonstrating that a sail can deploy reliably in orbit, that a gram-scale spacecraft can close the communications link from orbit to ground, and that deployers can be built from printed modular parts and consumer components are all necessary steps on that path. Each of those boxes has now been checked by a student laboratory.

The Space Systems Design Studio, a lab within Cornell’s Sibley School of Mechanical and Aerospace Engineering run by Professor Mason Peck, focuses on exploiting spacecraft physics to improve space capabilities, and these missions exemplify that philosophy. With both experiments having completed all major objectives, the results published through the Small Satellite Conference proceedings, and a pipeline of students trained on flight hardware, Cornell has established that free-flying light sails are no longer a paper concept. The pizza-box sail and its chip-sized passenger have flown, talked to the ground, and come home with data, and the next generation of sails is already being designed to steer, climb, and eventually ride beams of light far beyond Earth.

Subject of Research: Orbital deployment of free-flying light sails carrying gram-scale ChipSat spacecraft

Article Title: Cornell University successfully deploys free-flying light sails in orbit

Article References: Cornell University successfully deploys free-flying light sails in orbit. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: light sails, ChipSats, CubeSat, Alpha CubeSat, Sailing to the Stars, Cornell University, solar propulsion, low Earth orbit, ISS National Laboratory, Breakthrough Starshot, 3D-printed spacecraft, student space missions

The study, published in Space: Science & Technology by researchers from Politecnico di Milano, examines whether LUMIO — the Lunar Meteoroid Impacts Observer, a 12U CubeSat developed within the European Space Agency — could be repurposed, or rather have its mission extended, to observe Apophis during and after the close encounter. LUMIO is planned for deployment into a quasi-halo orbit around the Earth-Moon L2 point, a gravitational balance region beyond the Moon where a spacecraft can maintain its position with modest station-keeping. Its primary science goal is to detect the brief flashes of light produced when meteoroids impact the lunar farside, a phenomenon invisible from Earth. Launch is expected in 2028, meaning that if the mission is still operating in April 2029, the spacecraft would be ideally positioned for an entirely different kind of target.

The geometry is strikingly favorable. Approximately 19 hours after skimming past Earth, Apophis will itself pass at close range to the Moon, and LUMIO, hovering near L2, will have a vantage point from which the receding asteroid remains visible long after it has slipped out of view for ground-based observatories. This matters because most of the massive observational campaign planned for the flyby — radar installations, optical telescopes, and a fleet of space missions — will be concentrated on or near Earth. As Apophis rapidly recedes, ground-based observers will face blind spots precisely during the hours and days when the asteroid’s post-encounter condition, altered by Earth’s tides, may be most revealing. A camera at L2 could help fill that gap.

But feasibility was far from obvious, and the Italian team framed their analysis around three critical questions. First, can LUMIO-Cam, an instrument designed to catch transient impact flashes rather than faint moving asteroids, actually detect Apophis as a sub-pixel target — a point of light occupying less than a single pixel on the detector? Second, can it resolve fluctuations in the asteroid’s light curve, the subtle brightening and dimming that reveals how the body is tumbling? Third, can it observe for long enough to capture complete spin-period information, which is essential for diagnosing how the flyby changes the asteroid’s rotation state? Answering these questions required a detailed radiometric model of the entire imaging chain, from sunlight striking the asteroid’s surface to electrons accumulating in the camera’s silicon.

The signal model built by the researchers accounts for three distinct illumination sources. The dominant one is direct sunlight reflected by Apophis toward the camera. The other two are more exotic: Earthshine, sunlight reflected off Earth and then bounced from the asteroid’s surface toward L2, and lunar albedo, light reflected from the Moon’s surface before striking Apophis and finding its way to the detector. On the noise side, the model incorporates a formidable list of contaminants: dark current generated thermally within the sensor, readout noise introduced when the charge is converted to a signal, photon shot noise inherent to the light itself, quantization noise from digitization, the cumulative glow of background stars, and stray light scattered within the optics. The team validated the model by comparing its calculations against synthetic images produced by a physically based rendering engine, confirming the accuracy of the predictions.

To translate signal and noise into practical observing plans, the researchers defined three evaluation windows with precise criteria. The detection window requires a signal-to-noise ratio of at least 10, the conventional threshold at which a source can be reliably distinguished from the background. The sensitivity window is more demanding: the difference in signal between the upper and lower size limits of the asteroid’s brightness variation must exceed the number of electrons corresponding to one gray level of the camera, ensuring that fluctuations in the light curve can actually be resolved rather than lost in digitization. The scientific window is defined as the intersection of the two — the period during which Apophis is both detectable and photometrically resolvable. It is this third window that determines whether real science can be done.

The quantitative results are encouraging. Under optimal camera settings of gain 1000 and an exposure time of 2 seconds, the detection window in the visible channel can last up to nearly 30 days before the flyby, and the near-infrared channel performs comparably, approaching 30 days as well. That duration far exceeds the time needed to observe a full rotation of Apophis, which the study places at approximately 30.56 hours before the encounter and roughly 21 hours after. In other words, LUMIO could accumulate many complete spin cycles of photometry in the weeks leading up to the flyby, building a robust baseline against which post-encounter changes could be measured.

Saturation — the risk that the asteroid’s signal overwhelms the detector’s full well capacity when Apophis is at its brightest — emerges as a manageable challenge. The sensitivity analysis shows that under high gain settings the camera would indeed saturate around the time of closest approach, but by appropriately selecting gain 1 with a 2-second exposure time, saturation can be avoided while preserving the ability to resolve light-curve fluctuations. The scientific window under optimal settings can reach several hundred hours before the flyby. Critically, the post-flyby outlook is also viable: after the encounter, the visible channel can still provide approximately 1.5 spin periods of usable observation, equivalent to about 31.5 hours of window, at gain 1000 and an exposure time of roughly 0.06 seconds. That post-encounter coverage is exactly what ground-based observers will struggle to obtain, and it is where evidence of tidally induced changes in spin state or surface material migration would be most valuable.

The study also points toward a hardware upgrade path. If LUMIO were to adopt a CMOS detector in place of its CCD, the resulting shorter exposure times and higher readout speeds could further enhance observational performance, easing the saturation constraints and improving the cadence of photometric measurements. While the current analysis is based on the camera as designed, the finding suggests that even modest detector improvements could expand the scientific return from a platform whose primary mission was never aimed at asteroids at all.

For the planetary defense community, the implications extend beyond a single asteroid. Apophis’s 2029 flyby offers a rare chance to study tidal interactions, spin-state variations, and surface material migration on a near-Earth body as it happens, and the study demonstrates that a small spacecraft in cislunar space can provide complementary observational data from a perspective no ground telescope can match. As space agencies finalize their observing strategies for April 2029, the Milan team’s work offers a concrete, quantitatively grounded case for keeping a meteor-watching CubeSat alive a few months longer — and for considering Earth-Moon L2 as a standing vantage point in the planetary defense toolkit.

Subject of Research: Feasibility of observing asteroid Apophis's 2029 Earth flyby with the LUMIO CubeSat from the Earth-Moon L2 point

Article Title: Observing Apophis's 2029 flyby from earth-moon L2 with LUMIO

Article References: Observing Apophis's 2029 flyby from earth-moon L2 with LUMIO. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Apophis, LUMIO, Earth-Moon L2, planetary defense, near-Earth asteroids, CubeSat, light curve, radiometric modeling, signal-to-noise ratio, ESA, Space Science and Technology, 2029 flyby

The work, carried out by Mert Karahan, Nazmiye Selvi, and Onur Battal of the Electronics and Communication Engineering Department at the Turkish Military Academy of the National Defence University in Ankara, introduces what the authors call the Optimized Reflector-Integrated CPW-Fed Antenna, abbreviated ORICPW-FA. The device is contained entirely within a standard 1U CubeSat structural frame, the basic 10-centimeter cube unit of the CubeSat standard, and is intended to fly as a communication payload on larger multi-unit spacecraft such as 3U and 6U platforms. Critically, it respects the 6.5-millimeter rail-protrusion limit that governs how far any component may extend beyond the satellite’s structural rails before launch.

The trade-off the researchers set out to resolve is a familiar one in small-satellite engineering. Fixed-profile antennas, which keep a constant shape throughout the mission, are mechanically robust but typically offer limited bandwidth, meaning they can only operate efficiently over a narrow slice of the radio spectrum. Deployable antennas, by contrast, can unfold into large reflecting structures that deliver high gain and wide bandwidth, but they introduce hinges, springs, and release mechanisms that add mass, cost, and above all risk. A deployment that fails leaves the mission mute, and every additional mechanism is another point of failure that must be qualified for the vibration, vacuum, and thermal extremes of launch and spaceflight.

ORICPW-FA sidesteps that dichotomy with a hybrid architecture. At its core is a coplanar waveguide-fed radiating element, a feeding technique in which the signal-carrying conductors lie in a single plane on the substrate, which simplifies fabrication and keeps the feed compact. That element sits inside a cavity-backed structure, a metallic enclosure that shapes the radiation pattern, suppresses unwanted backward radiation, and stabilizes performance across frequency. The novel ingredient is what happens behind the radiator: a motorized reflector whose height above the radiating element can be adjusted in flight. By moving this reflector, the antenna effectively reconfigures its own electromagnetic environment, shifting the frequency range over which its beam remains stable and well-formed.

The physics behind this tuning is rooted in how the reflector modifies the boundary conditions seen by the radiating element. The distance between a radiator and its backing reflector determines how the direct and reflected waves combine, which in turn shapes the antenna’s impedance, its gain, and the directionality of its beam. In a conventional design that distance is frozen at manufacture. In ORICPW-FA, a small motor adjusts it on command, allowing the spacecraft to sweep the reflector position until the antenna presents the best possible pattern at whatever frequency the mission requires at that moment. The result, according to the authors’ full-wave simulations, is a dramatic widening of the usable band: pattern-stable operation extends from 6.0 to 8.2 gigahertz in a fixed-reflector reference configuration to a continuous 6.0 to 9.4 gigahertz once the reflector height is tuned.

Those simulation results come with performance guarantees that matter to mission planners. Across the tuned range, the antenna maintains a maximum main-lobe deviation, the amount by which the beam’s pointing direction drifts, of no more than plus or minus three degrees, and a sidelobe level of at most minus twelve decibels. Main-lobe deviation matters because a communication beam that wanders off target wastes link margin and can drop contacts with ground stations, while high sidelobes scatter transmitted power into unwanted directions and make the satellite more susceptible to interference. Holding both parameters within tight bounds across a 3.4-gigahertz span, covering the C-band and much of the X-band, is what makes the concept attractive as a genuine payload rather than a laboratory curiosity.

To confirm that the simulated behavior survives contact with reality, the team built a laboratory prototype and measured it at three representative tuning states: 7.0, 7.8, and 8.6 gigahertz. The measurements relied on S11 reflection-coefficient tests, which characterize how efficiently the antenna accepts power from its feed, and on time-domain-gated radiation-pattern measurements, a technique that filters out reflections from the surrounding test environment so that the antenna’s true pattern can be isolated. The measured peak realized gains came in at 8.41, 7.78, and 7.58 decibels relative to an isotropic radiator at the three frequencies respectively, while the measured patterns showed main-lobe deviations between zero and three degrees and sidelobe levels of minus 17.6, minus 18.9, and minus 14.6 decibels.

Those numbers support the central claim of the paper: that a moving reflector inside a cavity can genuinely steer an antenna’s operating characteristics in flight, without any part of the structure needing to unfold beyond the satellite’s envelope. The authors are careful to delineate the boundaries of their validation. The laboratory campaign confirmed pattern behavior at three representative tuning states, but continuous full-band radiation-pattern validation and space-environment qualification, the punishing sequence of thermal-vacuum, vibration, and radiation tests that any flight hardware must endure, remain outside the scope of this study. That is a standard and honest caveat for an early-stage design, and it marks the path from a working prototype toward a qualified flight unit.

The broader context explains why the result resonates beyond a single antenna design. CubeSats have evolved from educational novelties into serious platforms for Earth observation, technology demonstration, and even deep-space missions, and their communication demands have grown accordingly. A 3U or 6U spacecraft carrying ORICPW-FA could, in principle, retune its downlink or uplink frequency in orbit to match different ground stations, adapt to changing mission phases, or dodge interference, all with a single antenna that occupies one cube unit and never deploys. The design also speaks to a growing trend in antenna engineering toward reconfigurability as an alternative to sheer aperture: rather than making the antenna bigger, make it smarter about where and how it radiates.

There are, of course, engineering questions that follow hardware into orbit. The motor and its control electronics introduce their own reliability considerations, and the long-term behavior of a moving mechanical assembly in vacuum will need to be demonstrated before the concept earns a place on a flight manifest. But the study’s core demonstration stands: a deployment-free, motorized, cavity-backed antenna that fits the strictest CubeSat form factor while spanning C- and X-band with stable, well-controlled beams. For mission designers weighing the risk of deployables against the limits of fixed antennas, ORICPW-FA offers a third option, one in which the antenna tunes itself instead of unfolding, and the satellite keeps talking no matter what frequency the mission demands.

Subject of Research: A deployment-free, motorized frequency-reconfigurable cavity-backed CPW-fed antenna for C- and X-band CubeSat communications

Article Title: A Deployment-Free, Motorized Frequency-Reconfigurable Cavity-Backed Antenna for C- and X-Band CubeSats

Article References: A Deployment-Free, Motorized Frequency-Reconfigurable Cavity-Backed Antenna for C- and X-Band CubeSats. (n.d.). https://doi.org/10.1007/s42405-026-01281-w

Image Credits: AI Generated

DOI: 10.1007/s42405-026-01281-w

Keywords: CubeSat, antenna design, frequency reconfigurable antenna, cavity-backed antenna, CPW-fed antenna, motorized reflector, X-band, C-band, small satellites, satellite communications, deployment-free mechanism, aerospace engineering

Hera launched on October 7, 2024, and will become the first mission ever to rendezvous with a binary asteroid system. It is also the first multi-satellite expedition devoted to deep-space asteroid exploration. The stakes are high because NASA’s DART spacecraft slammed into Dimorphos on September 26, 2022, deliberately altering the moonlet’s orbit as a test of planetary defense. Hera, together with Milani and its sibling CubeSat Juventas, will survey the impact site and characterize the system in unprecedented detail. Milani’s trajectory design is aggressive for a six-unit CubeSat, involving a cascade of maneuvers through three main phases: a roughly three-week Far-Range Operations Phase for global mapping, a four-week Close-Range Operations Phase for close-up observations of Dimorphos and the DART impact site, and an Experimental Phase in which the satellite descends along a self-stabilized terminator orbit and eventually attempts a landing on Dimorphos.

The NavCam itself is a study in pragmatic engineering. Its optical head, designed and coated by Optec SpA, uses three lenses that hold focus at infinity with distortion below one percent, delivering an average transmissivity above 90 percent across the visible spectrum and a focal length of 12.96 millimeters. A coating on the first lens blocks wavelengths beyond 700 nanometers, shielding the detector from near-infrared leakage. At its heart sits a 1/3-inch CMOS rolling-shutter sensor from Onsemi, fitted with an RGB Bayer filter and an array of 2048 by 1536 pixels, each 2.2 micrometers square. That fine pixel pitch yields an instantaneous field of view of 35 arcseconds and a field of view spanning 19.72 by 14.86 degrees. In practical terms, the camera resolves 1.7 meters per pixel at 10 kilometers and a remarkable 8.5 centimeters per pixel at 500 meters, comfortably covering observation distances from 30 kilometers down to 200 meters.

Before any of that can happen, the camera had to earn its flightworthiness on the ground. Calibration at the Budapest University of Technology and Economics, the same facility that calibrated Hera’s instruments, covered bias and dark frames, bad-pixel identification, flat fields, linearity, radiometric response and distortion. The results are striking for such a small instrument: dark and bias frames show a uniform noise pattern with a standard deviation of only about 0.6 digital numbers, with no significant drift across exposure times, thanks to on-chip black-level correction. Flat-field correction removes strong vignetting, a 50 percent intensity drop toward the frame edges, and achieves better than 1 percent uniformity, while absolute radiometric uncertainty comes in under 2.5 percent. Distortion near the edges can shift star positions by as much as 50 pixels, but radial correction handles most of it, and in-flight starfield imaging against the Hipparchos and Tycho catalogs is expected to tighten the residual uncertainty from about 1.5 pixels down to 0.1 pixels.

The operations plan turns those optics into science. Data acquisition profiles, generated from the latest operational SPICE kernels, show that Milani will enjoy viewing geometries unavailable to Hera or Juventas, sampling a wide spread of phase angles that is crucial for surface characterization. By the team’s cumulative accounting, the NavCam can operate for 37 days with ground sampling better than 2 meters per pixel on Dimorphos, compared with 20 days for Hera’s Asteroid Framing Camera over the same window and 61 days for Juventas’ camera along its terminator orbit. Roughly 200 megabytes of asteroid imagery, compressed losslessly onboard with JPEG2000, will be downlinked over the mission, amounting to about 540 images or one picture every four hours on average. Each frame serves triple duty: orbit determination, flight dynamics reconstruction, and science.

The scientific payoff begins with global properties. Pre-impact models pictured Didymos as a top-shaped body like Bennu or Ryugu, but DART’s own DRACO camera revealed a surprisingly different silhouette, with a pronounced equatorial bulge and a shorter polar axis. Because DART’s observations are biased toward one hemisphere, Milani’s NavCam will help fill in the far side, contributing to high-resolution shape models built through stereophotoclinometry, a technique that fuses limb observations with landmark-based surface maplets. Those shape models cascade into bigger questions: how binary asteroids form, how the thermally driven binary YORP effect slowly reshapes their spins and orbits, and how much the DART impact deformed Dimorphos itself, which carries direct implications for assessing the efficiency of kinetic deflection. Combined with the Juventas radar’s mass and interior measurements, NavCam-derived shapes will also let the team test whether Didymos and Dimorphos share a uniform density or hide internal heterogeneity.

Surface science is the second pillar. The NavCam’s RGB channels cover roughly 400 to 700 nanometers, complementing the ASPECT hyperspectral imager on the same CubeSat, which works from 650 to 2500 nanometers, and providing color where Hera’s panchromatic Asteroid Framing Cameras offer finer resolution but no spectral information. To test what the camera can detect, the team convolved known mineral spectra from the RELAB database with the measured RGB response curves and ran k-means clustering on simulated measurements of asteroid Bennu, using spectra recorded by OSIRIS-REx’s OVIRS instrument. The clustering recovered distinct surface groups that overlap with earlier spectroscopic mapping, suggesting the camera can discriminate materials on Didymos and Dimorphos. Simulations of shocked anorthosite and irradiated ordinary chondrite add nuance: shock darkening changes reflectance uniformly across wavelengths and will be nearly invisible in color ratios, but space weathering reddens surfaces enough to raise the red-to-blue ratio by roughly 12 percent, a signal well within the camera’s reach. Mapping that ratio across the two asteroids could reveal freshly exposed impact ejecta and trace the system’s exposure age.

The camera will also feed gravity science. The University of Bologna leads Hera’s Radio Science Experiment, which fuses Earth-based tracking, inter-satellite links and optical images to estimate the asteroids’ mass, gravity harmonics and moments of inertia. NavCam images, taken from orbital geometries that differ from Hera’s, add independent constraints on the spacecraft-asteroid relative state, and tracking data collected during the final descent and landing will pin down the local gravity field near Dimorphos. The team even quantified the detectability of orbiting debris: one- and ten-centimeter particles should be visible across a useful range of distances and phase angles, echoing OSIRIS-REx, where tracking Bennu’s natural ejecta sharpened that asteroid’s gravity estimate dramatically.

Finally, the NavCam fronts Milani’s headline technology demonstration, the Autonomous Optical Navigation experiment. Milani’s vision-based guidance, navigation and control system, developed at Politecnico di Milano, computes asteroid centroids onboard to steer the spacecraft without relying on Earth. A dedicated Navigation Experiment Operation Centre in Milan will opportunistically compare the onboard navigation solution against a more precise, landmark-based ground reconstruction, testing the image-processing algorithms, the onboard estimator’s covariance, and even the GNC state machine’s ability to switch modes autonomously. In a closing twist, fictitious maneuvers computed from the onboard knowledge will be propagated in simulation and scored against the mission’s official flight dynamics solution, effectively rehearsing a fully closed-loop autonomous guidance cycle. For a CubeSat priced at a fraction of a flagship mission, the NavCam’s blend of navigation muscle and legitimate science makes a compelling case that the future of asteroid exploration may be very small indeed.

Subject of Research: The scientific operations and calibration of the Milani CubeSat's navigation camera aboard ESA's Hera mission to the Didymos binary asteroid system.

Article Title: The Scientific Operations of Milani NavCam

Article References: Ferrari, F., Fodde, I., Piccolo, F., Giordano, C., Rizza, A., Cremasco, A., Panicucci, P., Civati, L. F., Califano, P., Pugliatti, M., Topputo, F., Cardi, M., Pavoni, M., Calvi, D., Zanotti, A., Corradino, F., Kovacs, G., Palomba, E., Dirri, F., … Michel, P. (2026). The Scientific Operations of Milani NavCam. Space Science Reviews, 222(6), Article 73. https://doi.org/10.1007/s11214-026-01327-1

Image Credits: AI Generated

DOI: 10.1007/s11214-026-01327-1

Keywords: Milani, NavCam, Hera mission, Didymos, Dimorphos, DART impact, CubeSat, planetary defense, autonomous navigation, asteroid science, Space Science Reviews, stereophotoclinometry