3) Loaded dynamics. Settle time and wind response
What matters is not unloaded stiffness. It is the resonant behavior with payload installed. When loaded resonance is high, the structure can respond quickly enough for the control loop to reject wind and settle rapidly after moves. That is what protects cadence and keeps the image stable during real passes.

Learn More: Resonant Frequency - Loaded dynamics, settle time, and wind response.

4) Passive focus stability. Higher uptimeFocus stability is not a feature to “add later.” It is a duty-cycle amplifier. Passive stabilization reduces temperature-driven drift so long sequences run without repeated refocus interruptions, preserving PSF shape and centroid consistency.

Learn More: Focus Stability - Reduced refocus overhead, preserved PSF consistency, higher uptime.

5) Deterministic control and maintainabilityHS systems use a standardized control environment that supports repeatable acquisition, stable tracking, and long-term sustainment across a fleet. The result is a deployable sensor architecture that can be operated consistently across sites and programs.

Learn More: Modern Telescope Control with TCSGalil - Repeatable acquisition, stable tracking, maintainability.

ALT-ALT mount and drive architecture

Hemispheric field of regard

The HS series uses a true ALT-ALT double horseshoe geometry providing continuous hemispheric access with no meridian flips or zenith blind zones. There are no instrument pole obstructions that cut into usable sky. Alignment and commissioning are simplified compared to equatorial systems.

For imaging focused SDA missions, this means uninterrupted coverage along orbital arcs, predictable tracking behavior over the full sky, and more efficient use of clear time.

Torque motor plus high efficiency precision traction drive

HS-26 combines direct-drive torque motors with a backlash-free, high efficiency precision traction drive interface. The traction drive ratio introduces an effective mechanical ratio between the motor and the telescope axes, improving inertia matching while maintaining continuous rolling contact with no gear teeth and no backlash. 

This enables smooth, predictable energy exchange in both directions. Energy is added efficiently during acceleration and removed cleanly during deceleration and disturbance rejection.  Unlike pure 1:1 direct drive systems, this architecture supports fine low-speed control while preserving high-rate slewing capability. Small velocity and torque changes are realized as continuous motion rather than quantized steps, resulting in smooth tracking, fast step-and-settle performance, and low jitter under real wind and payload conditions.

• Learn More:  Precision Traction Drive Benefits

Structural dynamics as a complete system

The HS-26 features high structural stiffness with a measured ~10 Hz natural resonance for the complete system (mount, OTA, and payload).  This allows the control loop to operate with several hertz of usable bandwidth without exciting structural modes. Disturbances produce small, rapidly decaying motion rather than slow oscillation, enabling precise tracking, short settle times, and stable imaging under real environmental conditions.

• Learn More:  Bandwidth that shows up at the focal plane.

Optical system and detector

HS-26 uses ATLAS-derived fast survey optics at f/1.7, from the same wide-field optical family as LEO Scope, configured specifically for imaging performance. It delivers wide-field, corrected imaging onto a 60 mm × 60 mm CMOS focal plane, producing high étendue sensitivity at cadence with measurement-grade PSF behavior maintained across the field.

At f/1.7, focus stability is a system requirement, not an operational convenience. HS-26 maintains consistent focus through low-expansion optics and mechanically stabilized optical spacing, preventing temperature-driven drift during long exposures and extended runs. The result is stable PSF shape, centroid accuracy, and photometric consistency without relying on frequent refocusing.

Together, this optical and detector combination lets HS-26 image faint objects with short exposures to support fast-moving targets, then integrate efficiently to reach deeper magnitudes for characterization, light-curve analysis, and detailed follow-up.

Multi band imaging

An optional 8 position filter cassette system supports multi band imaging without complex external mechanisms. Fully integrated with remote and autonomous operation, it enables color photometry, proxy spectral classification strategies, and repeatable filter changes under unattended control.

Control system and encoders

HS-26 uses the Galil-based TCSGalil motion platform and TCSGO^TM software that power DFM’s SDA class systems, including GEODSS modernization and HS-16.

Standard control elements include:

• Renishaw 26 bit absolute encoders mounted directly on axis for both elevation axes
• Servo loops closed directly on absolute encoder feedback for minimal latency
• Integrated pointing model tuned for the HS series geometry and payload
• Trajectory feed-forward for satellite tracking and moving-target imaging
• Closed-loop tracking with compensation for flexure and gravity sag

Benefits:  Sub arcsecond repeatability for long exposures and precise object measurements, immediate recovery after power interruptions without homing, fast step and settle multiple target tasking, and long term maintainability decoupled from specific PC hardware cycles.

Use Cases

SDA imaging and characterization

• Full-frame imaging for LEO custody with scene awareness
• High signal-to-noise imaging of key objects for object identification and state assessment
• Deep imaging campaigns for faint debris or distant targets
• Light curve and temporal behavior studies for anomaly detection and classification

Optical ground station and lasercom support

• High-quality imaging of terminals and satellites for alignment and diagnostics
• Co-located imaging node in an OGS stack, leveraging ALT-ALT hemispheric coverage
• Testbed for multi-band observation strategies that inform operational link planning

Research and survey science

• Time domain science in survey fields as a by product of SDA operations
• Calibration work that supports model development and algorithm validation
• Collaborative campaigns with other wide field systems in planetary defense and variable object studies

Integration and deployment

HS-26 was designed for both fixed-site observatories and mobile nodes.  It is compatible with DFM roll on / roll off shelters for fixed sites.  It is also the largest DFM telescope that can be integrated with the mobile OGS trailer for off-road capable deployment.  The ALT-ALT geometry simplifies installation and alignment at remote sites.  The system supports autonomous operation and remote monitoring for sustained campaigns.

For programs, this means a single HS-26 configuration can serve as a fixed survey node at one site and as a mobile asset at another, sharing spares, control concepts, and sustainment practices across the network.

• Learn More: Domes That Protect Delivered Image Quality (DIQ): Why enclosure thermal behavior can dominate DIQ
• Learn More:  Optical stability is throughput

Mission alignment

If your concept of operations demands deployable aperture without giving up image quality, start with a system designed to field, align, and sustain predictably. HS-26 brings deep sensitivity and wide-field imaging into a package that can serve fixed sites or mobile deployment.

• Request a technical briefing on HS-26 performance and configuration options
• Explore how HS-26 and LEO Scope^TM can be combined in a tiered network of imagers and custody nodes
• Discuss mobile OGS integration for programs that need large aperture imaging in a deployable package

DFM Engineering builds HS-26 for teams that measure success by the quality and quantity of data they can collect over years of operation, not just by first year cost.