October 22, 2016 - China Launches Satellite for Climate Research

On October 22, 2016, China launched TanSat, its first dedicated carbon dioxide monitoring satellite. You can think of it as China's answer to NASA's OCO-2 and JAXA's GOSAT — a way to track CO2 levels without depending on foreign data. TanSat orbits in a sun-synchronous path, collecting roughly 100,000 daily soundings at 1 × 2 km resolution. There's a lot more to this mission than a single launch date.

Key Takeaways

• China launched TanSat, its first CO2-monitoring satellite, on October 22, 2016, to independently track atmospheric carbon dioxide for climate research.
• TanSat operates in sun-synchronous low Earth orbit, crossing the equator at approximately 13:30 local time while collecting reflected sunlight.
• The satellite's Carbon Dioxide Spectrometer measures CO2 absorption at 1.61 μm and 2.06 μm, targeting ~1% retrieval precision (~4 ppm).
• TanSat produces roughly 100,000 daily soundings at 1×2 km resolution, comparable to NASA's OCO-2 satellite performance.
• China pursued independent satellite monitoring due to data sovereignty concerns and the need for province- and sector-level emissions data.

Why China Needed Its Own CO2 Monitoring Satellite

Before China launched its own carbon dioxide monitoring satellite in 2016, it had to rely on data from American and Japanese systems—data it couldn't fully control or tailor to its own policy needs. That dependence raised serious concerns about data sovereignty, since foreign datasets don't always align with China's regional priorities or policy timelines.

You can see why this mattered. China needed emissions data broken down by province, city, and industrial sector to make informed decisions on carbon budgets and development plans. Without its own satellite, it was working with someone else's lens.

Owning independent monitoring infrastructure also tied directly into energy security, giving Chinese policymakers the reliable, first-hand intelligence required to shape climate strategy without waiting on data controlled by foreign governments or agencies. Canada demonstrated a comparable principle decades earlier, when Anik A1's shaped beam coverage proved that a single domestic satellite could deliver tailored, sovereign communications across a vast national territory without dependence on foreign land-based infrastructure. As the world's largest emitter of greenhouse gases, China had a particularly urgent stake in developing its own tools to monitor, verify, and ultimately defend its climate commitments on the global stage. Its newer satellites, such as one launched in 2026, now carry instruments capable of combined active and passive greenhouse gas monitoring, representing a significant leap in independent observational capability.

TanSat's Instruments and What They Measure

TanSat carries two core instruments that work together to deliver accurate atmospheric CO2 measurements. The Carbon Dioxide Spectrometer (CDS) is the mission's primary tool, and its instrument capabilities cover three spectral bands. It measures CO2 absorption at 1.61 μm and 2.06 μm while also capturing oxygen absorption at 0.76 μm. These measurement targets let scientists retrieve column-averaged CO2 concentrations across the atmosphere.

The Cloud and Aerosol Polarimetry Imager (CAPI) supports CDS by correcting errors caused by clouds and aerosols. You can think of it as TanSat's quality-control layer. CAPI observes five spectral channels ranging from 365 nm to 1,654 nm with a 0.5 km spatial resolution across a 400 km swath. Together, both instruments measure CO2 mole fraction, cloud cover, and aerosol optical depth. TanSat was built by the Shanghai Institute of Microsystem And Information Technology and funded by China's Ministry of Science and Technology. The mission targets a retrieval precision of 1%, or roughly 4 ppm, enabling scientists to quantify regional CO2 sources and sinks with meaningful accuracy.

How TanSat Compares to NASA and JAXA CO2 Satellites

When China launched TanSat in 2016, it entered a field already occupied by two well-established missions: NASA's OCO-2 and JAXA's GOSAT. Satellite comparisons show TanSat holds its own. Its XCO2 bias versus OCO-2 stays within 0.47 ± 0.28 ppm, confirming it matches NASA and JAXA precision standards.

You'll also notice measurement overlaps working in science's favor. TanSat delivers roughly 100,000 daily soundings at 1 × 2 km resolution, rivaling OCO-2's sounding size while outpacing GOSAT-2's 10,000+ daily count. TanSat's seasonal spatial coverage reaches 3.5 times that of GOSAT.

Rather than duplicating effort, these missions reinforce each other. Together, TanSat, OCO-2, and GOSAT-2 build a more complete, year-after-year picture of global CO2 sources and sinks. Merging these multiple satellite datasets reduces overall uncertainty and refines the accuracy of long-term greenhouse gas records.

Beyond carbon dioxide, TanSat also contributes to solar-induced fluorescence research, where its SIF retrievals show global spatial agreement with OCO-2 across all seasons, with gridded differences remaining below 0.3 W m⁻² sr⁻¹ μm⁻¹.

How TanSat Turns Infrared Data Into Global Emissions Maps

Matching the precision of OCO-2 and GOSAT means little without a reliable method for turning raw light measurements into actionable emissions data.

TanSat relies on IAPCAS, a dedicated spectral inversion algorithm that extracts XCO2 dry-air mole fractions from backscattered sunlight across O2 and CO2 absorption bands. CAPI's cloud and aerosol corrections reduce retrieval errors before the data enters flux assimilation pipelines.

Scientists then feed those XCO2 values into a 4D-Var system paired with GEOS-Chem, inferring net ecosystem exchange from April 2017 through March 2018. That process cut prior flux uncertainties by 30–50%.

The resulting maps exposed emission hotspots across eastern China, eastern Europe, and the eastern US while revealing how Northern Hemisphere photosynthesis draws down CO2 each spring and summer. These findings were formally published in Advances in Atmospheric Sciences, extending the satellite's contribution beyond raw data collection into peer-reviewed climate science. Much like the parabolic mirror ignition method used at Olympia concentrates sunlight to a single focal point with measurable precision, TanSat's retrieval system focuses dispersed spectral signals into quantifiable carbon flux estimates.

TanSat operates in a sun-synchronous low Earth orbit, crossing the equator at approximately 13:30 local time each day while collecting observations across three viewing modes: nadir, glint, and target.

How TanSat Laid the Groundwork for China's Daqi CO2 Satellites

Although TanSat was a minisatellite operating a narrow 20 km swath, it proved that China could build, launch, and operate a dedicated CO2 monitoring mission that matched international standards. Its instrument integration and mission legacy directly shaped TanSat-2, scheduled for 2026:

• Wider coverage: 2,900 km swath replaces TanSat's 20 km
• Higher orbit: 7,000 km altitude enables near-daily global coverage
• Urban focus: 116.6° inclined orbit targets Northern Hemisphere cities
• Finer resolution: 500 m footprints resolve urban CO2 gradients
• Constellation plans: Morning and afternoon orbits improve temporal sampling

You can see how TanSat's validated algorithms, SIF capabilities, and cloud correction methods gave engineers the confidence to scale China's next-generation Daqi greenhouse gas monitoring program. TanSat operates in three scientific observation modes — nadir, ocean glint, and surface target — each collecting sunlight reflected by Earth to retrieve CO2 column measurements across different viewing geometries. This approach to coordinated, large-scale atmospheric data collection echoes the enduring value of observation networks first demonstrated by ground-based stations and later extended into space-based platforms essential for modern environmental monitoring. TanSat-2 will carry the DuSIFIS instrument, a dual-band SIF spectrometer covering 672–702 nm and 747–777 nm at 0.12 nm spectral resolution to map both red and far-red solar-induced chlorophyll fluorescence globally.