An IRST sensor — short for Infrared Search & Track — is a passive sensing system that detects and tracks targets by the infrared radiation they emit, rather than by transmitting a signal of its own. Because it receives instead of transmitting, an IRST sensor can build situational awareness without revealing its own position the way an active emitter would. An IRST sensor is the complete system built by defense integrators; at its core sits the infrared detector — which is where SCD comes in. The detector is the component that converts incoming IR radiation into the electrical signal the system tracks, and its quality — sensitivity, resolution, and size, weight and power footprint — sets the ceiling on what the whole IRST sensor can do.
Infrared Search & Track is one of the defense applications SCD’s detectors are built for, alongside missile seekers, missile warning systems, thermal weapon sights and reconnaissance. SCD brings over 40 years of accumulated experience in infrared detector development and manufacturing, with battle-proven heritage across defense and homeland-security programs.
4 Min Read | by Ganit Shter Bar Joshua
An IRST sensor places demanding requirements on its infrared detector. Three matter most for defense buyers:
These same requirements — sensitivity, resolution, and a tight SWaP envelope — are what separate a general-purpose imager from a true military-grade infrared detector suited to search-and-track duty.
IRST systems draw on both the mid-wave (MWIR) and long-wave (LWIR) infrared bands, and SCD builds cooled MWIR, cooled LWIR and uncooled LWIR detectors across both.
In the MWIR band, SCD’s HOT (High Operating Temperature) detector technologies — XBn (barrier detector) and HFM — operate at high operating temperatures of 150K and 120K, delivering lower SWaP and a long Mean Time To Failure compared with traditional cooled approaches. HFM — Hot Full MWIR — is SCD’s own term for its high-operating-temperature detectors covering the full 3.6–4.9µm mid-wave band, rather than a narrower sub-band slice. MWIR’s shorter wavelength also enables smaller optics and higher F-numbers than LWIR — a meaningful advantage when packaging an IRST sensor into a constrained platform. SCD’s MWIR line spans the Sparrow family — Sparrow VGA (640 × 512) in both XBn and HFM (3.6–4.9µm) and Sparrow HD (5µm pitch, 1280 × 1024) — and the BlackBird (BB) family, available in InSb, XBn and HFM across 1280 × 1024 and 1920 × 1536 formats, up to the Crane at 5µm pitch and 2560 × 2048 HFM. The KINGLET 640 (15µm pitch, 640 × 512) rounds out the line, with XBn spectral coverage in the 3.6–4.2µm range. Several detectors carry a multi-function ROIC with laser pulse detection (ALPD, TLRF) for combined imaging and ranging.
In the LWIR band, SCD offers cooled Type-II Superlattice (T2SL) detectors such as the PELICAN-D LW (15µm pitch, 640 × 512), alongside uncooled VOx micro-bolometer detectors including the Bird 640 (17µm, 640 × 480), the Bird XGA (17µm, 1024 × 768) and the Robin family of 12µm VOx products. LWIR maintains a high signal-to-noise ratio even under exceedingly cold weather conditions and offers improved atmospheric penetration through smoke, dust and fog — properties that keep an IRST sensor effective when the MWIR picture degrades.
The cooled-versus-uncooled choice is itself a SWaP-versus-performance trade, and a cost and design consideration at the system level, optics included: cooled detectors deliver faster, higher-sensitivity imaging, while uncooled micro-bolometers offer low SWaP-C for portable systems.
SCD’s defense portfolio spans the SWIR, MWIR and LWIR spectral ranges, in both cooled and uncooled configurations, giving an IRST integrator a single source across the bands a search-and-track system relies on. Highlights relevant to EO/IR sensor and seeker designs include:
An IRST (Infrared Search & Track) sensor is a passive system that detects and tracks targets by the infrared radiation they emit, without transmitting a signal of its own. The IRST sensor is the complete system built by defense integrators; at its core is an infrared detector, whose sensitivity, resolution and SWaP set the ceiling on what the whole system can do.
Three: sensitivity, resolution and SWaP. Low NETD lets the detector pick faint targets out of a complex background; higher pixel counts extend the range at which a target can be detected and tracked; and a tight Size, Weight and Power envelope governs where the sensor can be mounted. SCD’s defense detectors span formats from 640 × 512 up to 2560 × 2048 and are designed low-SWaP to reduce the overall size and weight of the system optics.
It is a SWaP-versus-performance trade, and a cost and system-design decision as well. Cooled detectors deliver faster, higher-sensitivity imaging, while uncooled VOx micro-bolometers offer low SWaP-C for portable systems. SCD builds both across the MWIR and LWIR bands — including HOT (High Operating Temperature) XBn and HFM MWIR detectors that run at 150K and 120K for lower SWaP, and cooled T2SL LWIR detectors that hold a high signal-to-noise ratio even in extreme cold.
For IRST, EO/IR sensor and missile seeker infrared designs, SCD’s HOT MWIR detectors are the starting point: the Sparrow HD (XBn & HFM, 5µm pitch, 1280 × 1024), the BB1280 (HFM, XBn and InSb, 10µm pitch, 1280 × 1024) and the MINI BLACKBIRD 1280 HFM (10µm pitch, 1280 × 1024), alongside the T2SL LWIR PELICAN-D LW (15µm pitch, 640 × 512). The right choice depends on the platform’s SWaP envelope, the required detection range, and whether the design calls for a cooled or uncooled architecture.
Backed by more than 40 years of battle-proven development and manufacturing, SCD supplies the defense and homeland-security detector building blocks behind IRST, missile-seeker and surveillance systems. To match a detector to an IRST sensor program, start with the MWIR and LWIR detector families and the SWaP, sensitivity and resolution targets your platform demands.
HOT MWIR detector with 5µm pitch
