How CIRiS Takes Earth's Temperature from Space
The backpack-sized CubeSat that could change how we monitor our planet's health
In the vast expanse of space, a revolutionary backpack-sized satellite is transforming how scientists measure Earth's temperature. The Compact Infrared Radiometer in Space (CIRiS) represents a remarkable technological achievement: packing sophisticated infrared imaging capabilities into a tiny 6U CubeSat no larger than a shoebox. Developed by Ball Aerospace with NASA funding, this miniature observatory demonstrates that big discoveries can come in small packages 7 .
For decades, monitoring Earth's surface temperature required massive, expensive satellites with complex cooling systems. CIRiS shatters this paradigm with its innovative uncooled infrared sensor and built-in calibration system, providing scientists with precisely calibrated thermal data at a fraction of the size and cost of traditional satellites 6 7 .
6U CubeSat format enables low-cost deployment
Uncooled sensor eliminates bulky cooling systems
Infrared imaging reveals an invisible world of temperature variations that hold critical information about our planet's health. Every object emits thermal radiation based on its temperature, and by measuring this infrared energy, scientists can detect patterns invisible to the naked eye .
Thermal infrared data serves as a vital tool for numerous Earth science applications:
Traditional infrared instruments require heavy cryocoolers to operate at extremely low temperatures, making them impractical for small satellites. CIRiS overcame this limitation through innovative engineering, proving that high-quality thermal data can be gathered without bulky cooling systems 7 .
At the heart of CIRiS lies a fundamental engineering challenge: how to achieve laboratory-grade precision in a device small enough to fit inside a CubeSat. The solution involved breakthroughs in multiple technologies working in harmony 6 .
CIRiS packs impressive technical capabilities into its small frame, as shown in its key specifications:
| Parameter | Specification | Significance |
|---|---|---|
| Platform | 6U CubeSat (≈10×22×36 cm) | Fits standard CubeSat dispensers; low cost deployment 6 9 |
| Focal Plane | Uncooled microbolometer 640×480 | Eliminates need for heavy cryocooler 6 7 |
| Infrared Bands | 3 bands between 7.5-13.5 μm | Optimized for Earth observation applications 1 |
| Ground Resolution | 160-166 m at 470-500 km | Detailed enough for agricultural and environmental monitoring 1 6 |
| Calibration Views | Deep space + 2 blackbody sources | Enables precise on-orbit calibration 1 6 |
The cornerstone of CIRiS' scientific value is its innovative calibration system, which ensures the accuracy of every temperature measurement. Unlike traditional satellites that may rely on ground-based calibration or limited space views, CIRiS features multiple calibration pathways using a scene select mirror that can direct the instrument's view to four different targets 1 6 :
For Earth observation and data collection
For cold reference calibration
With high-emissivity carbon nanotube coatings
The carbon nanotube blackbody sources are particularly innovative, with an exceptional emissivity greater than 0.9965, meaning they absorb and re-emit nearly all incident radiation 1 6 . This creates reliable reference sources for calibration. One blackbody can be set to specific temperatures, while the other remains at instrument temperature, providing multiple reference points to correct for instrument drift 6 .
Before CIRiS could journey to space, it underwent rigorous testing in laboratory conditions that simulated the space environment. The thermal vacuum (TVAC) campaign represented one of the most critical validation steps, where the entire integrated spacecraft was subjected to space-like conditions to verify performance and calibration 6 .
The TVAC testing followed a carefully designed procedure to push CIRiS to its operational limits 6 :
The system underwent extreme temperature cycles to verify all components, particularly survival heaters, would function properly under worst-case scenarios.
The instrument performed calibration measurements at progressively different temperature levels spanning the expected on-orbit range.
The system completed multiple thermal cycles at operational limits, demonstrating stability through simulated orbital temperature variations.
Throughout these tests, the team used a NIST-traceable blackbody calibration source—a laboratory standard with known accuracy—to verify CIRiS' temperature readings 6 . The calibration process involved comparing CIRiS' measurements against this reference standard under vacuum conditions, which eliminated atmospheric interference that would affect infrared measurements.
The TVAC testing yielded crucial validation data, demonstrating that CIRiS could maintain excellent radiometric performance even when subjected to the temperature extremes of space. The data collected showed that the calibration system could effectively transfer accuracy from the known reference sources to Earth-viewing measurements 6 .
Deep Space
Establish background reference
Multiple times per orbitControlled Blackbody
Reference to known temperature
Multiple times per orbitAmbient Blackbody
Reference to instrument temperature
Multiple times per orbitEarth
Science data collection
Primary mission operationPerhaps most importantly, these tests verified the functionality of the onboard calibration transfer process—the method by which CIRiS uses its deep space and blackbody views to maintain accuracy between ground calibrations 6 . This capability is essential for long-term monitoring missions where instrument response may gradually change over time.
CIRiS combines several advanced technologies that work together to achieve its miniature yet powerful design.
| Component | Function | Innovation |
|---|---|---|
| Uncooled Microbolometer FPA | Converts infrared energy to electrical signals | Operates without cryogenic cooling; reduces size and power 6 7 |
| Scene Select Mirror | Directs instrument view between targets | Enables multiple calibration views without moving entire satellite 1 6 |
| Carbon Nanotube Blackbody | Provides known temperature reference | Exceptionally high emissivity (>0.9965) improves calibration accuracy 1 6 |
| Onboard Processing | Performs data analysis and calibration | "Software performance replaces hardware performance" |
The uncooled microbolometer eliminates the need for power-intensive cryocoolers, making CIRiS ideal for small satellite platforms with limited power budgets.
By integrating multiple calibration views into a single compact instrument, CIRiS achieves laboratory-grade precision in a shoebox-sized package.
The success of CIRiS has already spawned new missions that build upon its technology. Lunar CIRiS (L-CIRiS) will use similar instrumentation to study the mineralogical composition and thermophysics of the lunar surface as part of NASA's Artemis program 1 7 . Another sibling instrument, Lunar VISE CIRiS, will be mounted on a lunar rover to provide calibrated infrared images of the Moon's surface 7 .
"Multiple CubeSats in orbit would allow us to measure changes in evapotranspiration and other phenomena potentially as often as every day."
Constellations of CIRiS-like satellites could revolutionize how we monitor crop health and optimize irrigation across global agricultural regions.
Early detection of thermal anomalies could help identify wildfire hotspots before they escalate into large-scale disasters.
Frequent thermal monitoring of reservoirs, rivers, and soil moisture could improve water allocation decisions in drought-prone regions.
Long-term temperature datasets from CIRiS constellations could provide valuable insights into climate change impacts at regional scales.
The potential applications extend far beyond these initial missions. David Osterman envisions constellations of CIRiS-like instruments orbiting Earth. Such constellations could revolutionize how we monitor drought conditions, manage agricultural water use, and track the impacts of climate change—all with unprecedented frequency and at lower cost than traditional satellite systems.
CIRiS represents more than just a technological achievement—it demonstrates a new paradigm for Earth observation where small, affordable satellites can deliver meaningful scientific data. By solving the challenge of miniaturized radiometric calibration, CIRiS has opened the door for future constellations of small satellites working together to monitor our planet's health 7 .
As we face growing challenges of water management, climate change, and food security, the type of frequent, precise thermal monitoring enabled by CIRiS technology will become increasingly valuable. This tiny satellite proves that when it comes to solving big problems, sometimes the most powerful solutions come in small packages.