NEOSSAT

NEOSSat — the Near Earth Object Surveillance Satellite — is a Canadian microsatellite launched on February 24, 2013, and operated by the Canadian Space Agency. Catalogued under NORAD ID 39089 and international designator 2013-009D, it occupies a sun-synchronous low Earth orbit and carries a small optical telescope designed to survey the sky for asteroids whose orbits keep them largely inside Earth's own orbital path around the Sun. Weighing just 74 kilograms, NEOSSat belongs to the microsatellite class, yet it pursues scientific objectives that would challenge instruments many times its size. As of the time of writing, the satellite remains in orbit and continues to be tracked.

Mission and Purpose

NEOSSat was conceived to address a specific and technically demanding gap in planetary defence science: the detection and cataloguing of asteroids whose orbits lie interior to Earth's — a population sometimes designated interior-to-Earth-orbit (IEO) objects. These bodies are notoriously difficult to observe from the ground precisely because doing so requires pointing telescopes at relatively small angular distances from the Sun, where daylight, atmospheric scattering, and the horizon itself conspire to obscure the sky. A space-based platform, free from both the atmosphere and the day-night cycle as it applies to ground observers, is far better suited to staring into the inner solar system.

The satellite's telescope is designed to search within a solar elongation window of roughly 45 to 55 degrees — that is, at angular separations from the Sun that ground-based instruments find almost unusable. The survey additionally spans an ecliptic latitude range of approximately plus to minus 40 degrees, giving it a meaningful swath of sky in which IEO candidates are most likely to be found. By systematically covering this observing window, NEOSSat can build a statistical picture of the inner asteroid population that complements the predominantly exterior-looking surveys conducted by ground observatories.

Funding for the mission came from two Canadian federal bodies: the Canadian Space Agency, which leads the civilian science mandate, and Defence Research and Development Canada, reflecting an interest in the dual-use value of space surveillance technology. Tracking small, fast-moving objects in difficult regions of the sky has obvious relevance both to planetary science and to broader space situational awareness — the ability to know what is sharing the near-Earth environment. This dual sponsorship shaped NEOSSat into a platform that could, in principle, contribute to both the scientific census of near-Earth objects and the operational awareness of objects in Earth orbit.

Design and Operator

NEOSSat was designed and built by Microsat Systems Canada Inc., a company with experience in small satellite development. The finished spacecraft has a launch mass of 74 kilograms, firmly in microsatellite territory and a testament to how capable small platforms had become by the early 2010s.

At the heart of the satellite is a Maksutov telescope with a 15-centimetre aperture and a focal ratio of approximately f/5.88. The Maksutov design — a catadioptric optical system using a combination of a meniscus corrector lens and a spherical primary mirror — is well suited to compact telescope packaging, delivering a relatively long effective focal length within a short physical tube. This makes it attractive for spacecraft where volume and mass budgets are tightly constrained. For a satellite dedicated to detecting faint, slow-moving points of light against a dense star field, optical quality and a clean point-spread function matter enormously, and the Maksutov configuration addresses these requirements without demanding a large instrument.

Attitude control is achieved through a three-axis stabilisation system. The spacecraft can hold its pointing to a stability of around two arcseconds over an exposure duration of roughly 100 seconds. This level of stability is critical for asteroid detection work, where the technique typically involves taking sequences of images and looking for sources that shift position relative to the background stars — a method that breaks down entirely if the telescope itself is drifting or jittering during an exposure.

The Canadian Space Agency, headquartered in Longueuil, Quebec, serves as the operating authority. Canada has a long history of contributing to space science through niche, high-value missions rather than large flagship observatories, and NEOSSat fits that tradition — small, focused, and targeted at a problem where it could make a distinctive contribution.

Orbit and Tracking

NEOSSat circles Earth in a sun-synchronous orbit, a class of near-polar orbit in which the orbital plane precesses at a rate that keeps it at a nearly constant angle relative to the Sun throughout the year. Sun-synchronous orbits are achieved by exploiting the oblateness of Earth — its slight equatorial bulge — to induce a steady eastward drift of the orbital plane that matches Earth's annual revolution around the Sun. For a remote sensing or surveillance satellite, this arrangement has the practical advantage of ensuring that the spacecraft passes over any given point on Earth at approximately the same local solar time on every orbit, maintaining consistent illumination conditions. For NEOSSat, the sun-synchronous geometry has a different benefit: it provides a stable, predictable relationship between the satellite's orbital plane and the direction of the Sun, which matters greatly for a telescope that must carefully manage which parts of the sky it can safely observe without risk of solar contamination.

The current orbital parameters place NEOSSat at an apogee of 784 kilometres and a perigee of 769 kilometres, yielding an orbit that is nearly circular with only about 15 kilometres separating its highest and lowest points. The orbital inclination is 98.4 degrees — slightly retrograde, as is characteristic of sun-synchronous orbits. The satellite completes one revolution around Earth every 100.2 minutes, meaning it executes roughly 14 to 15 orbits per day.

At these altitudes, atmospheric drag is very low but not entirely negligible over long time periods. The near-circular orbit helps in this respect, since a highly elliptical orbit would dip periodically into denser atmospheric layers and decay more rapidly. NEOSSat has remained in orbit continuously since its 2013 launch, and no reentry date has been recorded in the catalog.

NORAD catalog number 39089 serves as the spacecraft's permanent identifier in the Two-Line Element set system used by space-tracking organisations worldwide. The COSPAR international designator 2013-009D encodes its launch: the ninth launch of 2013, with NEOSSat being the fourth object catalogued from that launch event.

Significance and Status

NEOSSat was, at the time of its launch, a notable demonstration that microsatellites could be entrusted with serious scientific observation missions rather than being restricted to technology demonstration or educational roles. Its combination of a real astronomical instrument, precision attitude control, and a purpose-built survey strategy represented a meaningful step in the miniaturisation of space science hardware.

The asteroid population it targets — those on orbits interior to Earth's — remains one of the less-well-characterised groups of near-Earth objects. Ground surveys have catalogued tens of thousands of near-Earth asteroids, but the inner population is systematically underrepresented because of the observational barriers described above. Any object in this region that is on a trajectory capable of intersecting Earth's orbit represents a potential hazard that could approach from a direction that ground-based systems find difficult to monitor in advance. NEOSSat's vantage point in orbit offers a means of surveying this population more completely.

The mission's dual mandate — scientific survey combined with space situational awareness interests through Defence Research and Development Canada — also reflects a broader trend in small satellite missions during this period, in which civilian science goals and national security interests in the near-Earth environment increasingly overlapped. The ability to detect and track small objects, whether they are asteroids or resident space objects, draws on much of the same sensor technology and data-processing capability.

Mission status is not publicly recorded in the satellite catalog at the time of writing, and current operational details are not confirmed here. What is established is that the satellite's orbital elements continue to be tracked, and its object record remains active as a payload in low Earth orbit.

How to Spot NEOSSat

NEOSSat is a small satellite — 74 kilograms — and does not carry any large reflective panels or structures that would make it especially bright to a visual observer. It is not generally listed among satellites readily visible to the naked eye, and casual sky-watchers are unlikely to pick it out without optical aid. That said, in its 769–784 kilometre sun-synchronous orbit, it follows a predictable, near-circular ground track that repeats at consistent local times, making it in principle trackable using standard satellite prediction tools and a modest telescope or binoculars. Observers in mid-to-high northern and southern latitudes benefit from the near-polar inclination of 98.4 degrees, which carries NEOSSat over a large fraction of Earth's surface. Up-to-date Two-Line Element data sourced from the NORAD catalog and entered into satellite tracking software will give the most accurate predictions for any given location.