Tracking and Monitoring

Optical Measurement

NASA

Radar Measurements

The NASA Orbital Debris Program Office (ODPO) uses specialized ground-based radars. These radars don’t follow specific objects; instead, they statistically sample debris populations in low Earth orbit (LEO) that are too small to be tracked by standard military space surveillance networks but still pose a collision threat to spacecraft. The primary tools for this are three radar systems:

Haystack Ultrawideband Satellite Imaging Radar (HUSIR): NASA’s main source of data for debris between approximately 5 mm and 30 cm. It has been collecting data since 1990 using a “stare” method, holding a fixed pointing angle to detect objects passing through its field of view
Haystack Auxiliary Radar (HAX): Located alongside HUSIR, this less sensitive radar operates at a different wavelength (1.8cm) and has a wider field of view, providing complementary data
Goldstone Orbital Debris Radar: Extremely sensitive radar, operated by NASA’s Jet Propulsion Laboratory (JPL), is capable of detecting debris as small as about 2 mm in LEO. It can detect a 3 mm metallic sphere at a range of 1,000 km, making it crucial for characterizing the sub-centimeter debris population.

Optical Measurements

ODPO uses optical telescopes to passively measure sunlight reflected by debris. This method complements radar data and is essential for routinely observing objects in higher orbits, including the geosynchronous orbit (GEO) regime.

-Current and Primary systems for optical measurement:

Eugene Stansbery Meter-Class Autonomous Telescope (ES-MCAT): This is a 1.3-meter, fast-tracking optical telescope located on Ascension Island in the South Atlantic. Its equatorial location provides unique coverage of the GEO belt and very dark skies for detecting faint objects. Its primary goal is to statistically characterize the debris environment at all altitudes, with an emphasis on GEO, and it can be tasked for rapid response to in-orbit break-up events.
Optical Measurement Center (OMC): This is a ground-based laboratory that uses a solar simulator, a robotic arm, and spectrometer to analyze how simulated space debris materials reflect light. By creating and studying light curves of various spacecraft materials (like insulation, solar panels, and metals), the OMC helps scientists interpret the telescopic data to identify debris properties such as material type, shape, and rotation.
MODEST Telescope (Past Primary Optical Sensor): A 0.6-meter Schmidt camera, previously operated at the Cerro Tololo Inter-American Observatory (CTIO). From 2001 to 2014, MDOEST was NASA’s main telescope surveying debris at GEO. It routinely detected objects down to ~17.5 magnitude, and sometimes to ~18.3 magnitude, corresponding to tens of centimeters sizes at GEO. Its data helped build earlier versions of the orbital debris environment model, such as ORDEM 3.2

In situ measurements

This refer to direct sampling of impacts or debris effects in space, rather than observing debris from the ground with radars or telescopes. These techniques capture evidence of very small particles, often too tiny to be seen remotely, by examining physical damage on spacecraft hardware or by flying impact sensors directly in orbit.

-Hubble Space Telescope (WFPC-2)

NASA analyzed the radiator panel from the Hubble Telescope’s Wide Field Planetary Camera 2 after it spent about 16 years in low Earth orbit.
The large surface area acted like a collector plate, accumulating craters and impact marks from both micrometeoroids and human-made debris.
-Scientists extracted samples from this aluminum plate and examined them with electron microscopy and X-ray spectroscopy to distinguish particle origins and better understand the small-particle environment.

-Hubble Multi Layer Insulation (MLI)

Blankets of thermal insulation removed from Hubble were also studied for impact damage.
These layers showed both surface craters and full perforations. By examining these features with improved characterization techniques, researchers gain insight into the size and dynamics of the particles that struck the material.
This work helps improve estimates of debris flux and validate orbital debris environment models.

-Active in situ impact sensor: Space Debris Sensor (SDS)

NASA developed the Space Debris Sensor (SDS) as the first on-orbit demonstration of the DRAGONS sensor technology (Debris Resistive/Acoustic Grid Orbital NASA-Navy Sensor).
SDS was installed externally on the International Space Station (ISS) Columbus module in early 2018 to directly record small particle impacts in orbit.
Over its operational life, SDS gathered electrical resistance and acoustic data associated with impacts, proving the viability of the DRAGONS technology for measuring sub-millimeter debris.
While the mission was short and didn’t fully achieve all its characterization goals, it successfully demonstrated real-time detection and downlink of impact data from a spaceborne detector.

-Other curated impact evidence

In addition to Hubble surfaces, NASA curates materials from many spacecraft and missions that have returned to Earth with documented impact evidence. These include sample return capsules and hardware from missions such as Genesis, Stardust, Surveyor III, LDEF (Long Duration Exposure Facility), Solar Maximum Mission, EuReCa, and parts of the Mir space station. These archived surfaces serve as historical records of micrometeoroid and orbital debris (MMOD) impacts over long exposure times.

China National Space Administration (CNSA) + China Aerospace Science and Technology Corp (CASC)

-A research article provides a systematic assessment of China’s advancements in the science and applied technology of space debris over the two‑year span from 2020 to 2021. This period corresponds with the concluding phase of China’s 13th Five‑Year Plan and the early phase of the 14th Five‑Year Plan, both of which prioritize improvements in space environment governance and orbital safety. The work is explicitly aligned with the White Paper “China’s Space Program: A 2021 Perspective”, which frames space debris management as a core component of national space policy and long‑term sustainability.

-This includes the deployment and optimization of a network of ground‑based telescopes with varying apertures to improve detection and tracking of orbital fragments:

A 1.2‑meter aperture telescope with a wide field of view has been completed and is undergoing calibration for debris and near‑Earth object observation.

The Xinglong 60 cm telescope has been operational and is contributing to both orbital debris and asteroid surveys.

A 36 cm prototype telescope array is already in use for wide‑field surveys and synthetic tracking.

These assets contribute to higher precision in orbit determination, better characterization of debris populations, and enhanced early warning capabilities.

In addition, China is cooperating with regional observatories such as the Asia Pacific Space Science Observatory (APSSO) to expand the observational baseline and support joint campaigns on debris and near‑Earth object monitoring.

Chinese researchers have worked on advanced collision avoidance and prediction models. China has built unified databases that integrate tracking data and event history, enabling improved algorithms for conjunction assessments, re‑entry predictions, and anomaly analyses linked to satellites and rocket bodies.

As of 2022:

China had a patchwork of sensors linked to lunar and planetary exploration missions, but it did not yet operate a dedicated constellation designed to scan the entire region between geosynchronous Earth orbit (GEO) and the Moon for unknown objects.

Ground installations, such as optical telescopes and radio telescopes (including Very Long Baseline Interferometry networks) ,play a part in tracking known spacecraft and astronomical bodies. These systems can contribute to SSA, particularly for objects already cataloged, but are not optimized for discovering everything in deep space.

China’s deep space tracking network (its Deep Space Network and cooperating facilities overseas) supports communication with lunar and Mars probes, and these systems also contribute useful tracking data.

China has experimented with spaceborne optical and infrared sensors through missions such as the Chang’e lunar program. These instruments are capable of imaging and observing celestial and man-made targets, but were originally tailored more to mission-specific tasks than broad SSA scanning.

Micro-satellites (e.g., Longjiang-2) and other orbiting platforms have been used experimentally to expand SSA capabilities and test imaging or tracking techniques in space.

The Chinese government and scientific community have begun planning more comprehensive SSA capability expansion. Future systems discussed include wide-field optical and infrared satellites and dispersed constellations of sensors potentially placed at strategic locations (such as Lagrange points or heliocentric orbits) to discover and monitor previously unknown objects. Such systems would enable autonomous scanning beyond GEO, helping China better catalog space traffic and potential hazards.

Proposals mentioned include concepts for a multi-satellite “Near-Earth Object Heterogeneous Monitoring Constellation” (CROWN), involving a “mother and child” swarm of satellites, intended to improve autonomous detection and tracking of deep space objects.

China is developing a substantial space situational awareness (SSA) constellation, a new orbital monitoring network often referred to as “Xingyan” (“Star Eye”) or EYESAT. The system is designed to track objects in Earth orbit, detect debris and satellites, and support collision warnings and space traffic management.

Constellation will consist of 156 satellites covering multiple orbital altitudes to deliver near-continuous situational awareness
First launches: expected to being around 2026
Full deployment: planned for 2028 and beyond

China’s system is seen as complementary or competitive with other SSA efforts like the U.S. Geosynchronous Space Situational Awareness Program (GSSAP) and global debris tracking networks.

The Hybrid CoE Paper 21 describes how China has been investing significantly in space surveillance, tracking, and situational awareness capabilities.

China has been building up its space surveillance and tracking infrastructure—known as SSA/SST (Space Situational Awareness and Space Surveillance and Tracking). This includes radars and optical sensors primarily within its national borders, supplemented by tracking ships at sea. This SSA network supports monitoring satellites, debris, and space weather, and it underpins military and civilian space operations.

The document notes that China’s investment in SSA is partly aimed at concealing its own terrestrial military activities and enhancing intelligence gathering, including against foreign spacecraft.

Independent reporting confirms that China is developing at least two dedicated space situational awareness constellations:

The Guangshi/Kaiyun network (in early stages) with an initial group of satellites launched in 2025.

A more ambitious system called Xingyan (“Star Eye”), stated above.

In the LLNL paper, SSA is described not as a standalone scientific effort but as a component of China’s military and counterspace toolkit. It’s grouped alongside kinetic and non-kinetic counterspace systems, electronic warfare, and other capabilities that collectively enhance China’s ability to operate in and contest space.

SSA is explicitly included in a table of military space capabilities and defined as including ground-based optical telescopes and radars as well as satellites on orbit whose task is to monitor and track objects in space. This supports both intelligence collection and understanding of the space domain in ways that could benefit PLA operations.

The document states that SSA improves China’s visibility into the space domain, which can help it monitor other space powers’ assets and potentially inform PLA planning. At the same time, having a clearer picture of object locations could help protect China’s satellites by warning of potential threats or crowded orbital conditions—though the paper emphasizes the military applications more than purely safety functions.

Japan Aerospace Exploration Agency (JAXA)

-Direct imaging of fast-moving objects

JAXA’s research emphasizes direct optical imaging of large debris objects, using a dedicated telescope located at the optical observation facility on Mount Nyukasa in Japan. The primary tool is a 60‑cm aperture telescope designed specifically to capture clear images of orbiting debris as they traverse the sky. These observations are critical for accurately determining debris trajectory, rotation, and shape. The ability to image debris directly, rather than relying solely on indirect radar or catalog data, improves JAXA’s capability to characterize object motion in ways that support both predictive modeling and future active debris removal (ADR) mission design.

-Motion and light analysis

A central part of this research is interpreting the light curves and brightness variations of debris targets. When sunlight reflects off an object, subtle changes in brightness occur as it rotates or changes orientation. JAXA researchers employ simulated lighting experiments, using scale models and controlled illumination on the ground, to build reference data that help extract motion and attitude information from actual observational data captured by the telescope.
These techniques are enhanced with computer graphics (CG) simulation tools, which generate synthetic brightness data that can be compared against real observations. This combination of practical experimentation and simulation provides a strong foundation for interpreting debris behavior from limited optical data.

In April 2022, Fujitsu announced that it had developed and put into operation a new analysis system to support the Japan Aerospace Exploration Agency’s (JAXA’s) Space Situational Awareness System at the Tsukuba Space Center in Japan. This tool is designed specifically to track and predict the motions of space debris and help protect satellites in orbit.

• Precision orbit calculation:

Fujitsu’s system uses observational input from radar installations and optical telescopes to compute the orbital paths of debris and compare them with the locations of JAXA’s satellites. This allows operators to understand where debris is relative to active spacecraft.

• Collision risk assessment:

By automatically estimating the likelihood of close approaches or potential impact events, the system helps JAXA assess collision risks quickly. It can also assist in calculating maneuvers that satellites might need to avoid debris.

• Operational planning and automation:

The platform can generate optimized observation plans and automate routine data processing tasks that used to be done manually, helping reduce operator workload and improve efficiency in tracking many objects.

• Integration with government SSA networks:

The tool is built to interoperably share data with SSA infrastructure run by the Japanese government, enabling coordinated observation efforts and fulfilling external requests for tracking information.

An interview‑style feature from the Japan Aerospace Exploration Agency (JAXA) focuses on Japan’s Space Situation Awareness (SSA) efforts, particularly how JAXA monitors space debris and protects satellites from collisions. The article is based on insights from Mayumi Matsuura, Project Manager of JAXA’s SSA System at the Space Tracking and Communications Center (STCC).

-Observation Infrastructure:

The Kamisaibara Spaceguard Center uses ground‑based radar to observe debris in Low Earth Orbit (LEO) up to about 2,000 km altitude.

The Bisei Spaceguard Center uses an optical telescope to track objects in Geostationary Earth Orbit (GEO) at roughly 36,000 km altitude.

These systems can track objects 1 m and larger, though smaller debris (<1 m) remains harder to observe directly from Japan.

-Role of JAXA’s STCC:

JAXA collects and analyzes tracking data from these facilities to determine the orbits and positions of observed debris. When potential conjunctions (close approaches) with active spacecraft are identified, the STCC issues collision warnings to mission teams and provides detailed recommendations on how to avoid impacts, typically by adjusting the spacecraft’s orbit. In cases where a piece of debris is expected to re‑enter the atmosphere, JAXA also predicts the likely re‑entry location.

State Space Corporation Roscosmos (Russia)

-Russia is proposing a new global space surveillance and warning system called “Milky Way” (Млечный путь), intended to expand on its current capabilities for monitoring both artificial space objects (like satellites and debris) and natural hazards such as potentially dangerous asteroids and comets.

Russia’s existing system, ASPOS‑OKP, already monitors space debris and warns of close approaches for spacecraft, including the ISS, but it does not track asteroids or natural celestial threats.
Space‑based observation: The Milky Way project envisions placing a spacecraft near the Earth–Sun L1 libration point (~1.5 million km from Earth) to observe objects from a vantage point not blocked by the Sun’s glare, helping detect bodies approaching from the sunward side (where ground telescopes can’t see).

-Russia has pitched the Milky Way project as an international system. It would include:

Partners from BRICS (Brazil, Russia, India, China, South Africa, etc.), with shared access to data and measurements,

Open information platforms allowing participation by public and private organizations worldwide.

-Roscosmos officials have stated plans to launch the Milky Way system by the end of 2024 with an open information platform for collaboration