DFM Engineering, Inc.
1035 Delaware Ave. Unit D
Longmont, CO 80501
Phone: 303-678-8143
Fax: 303-772-9411

 
 
 

ATLAS - Optics Specifications

 
 
Lens Figuring

OPTICS REQUIREMENTS

The ATLAS optical tube assembly is specifically designed to detect asteroids and provide warning of an impact with the Earth.

Therefore the optics requirements are unique.

The ATLAS is specifically locating and tracking asteroids and is designed for long, continuous exposure segments to collect vast amounts of data. The only "at rest" period is dedicated to the download of collected data to the control system. After which, the ATLAS resumes tracking and data collection.

mirror polishing
Mirror Polishing

As a result, it is imperative the optics are very fast and precise. Quality data collected is a direct result of quality optics.

The two Optical Tube Assemblies and their corresponding control systems work in tandem to cover a vast sky area providing a significant blanket of coverage with corresponding data sets.

optics testing
Optics Testing

ATLAS Components Considerations

The following components considerations are noted as they pertain to the optics of the ATLAS.

Coatings Comparisons:
Utilizing a broad band AR coating reflection curve was compared to an enhanced aluminum coating curve. The study revealed the enhaced aluminum reflectance coating provides an average reflectance greater than 90% between 400 and 850 nm.

enhanced aluminum curve diagram
Reflectance vs. Wavelength Enhanced Aluminum Curve Diagram

Environmental Conditions:
Temperature range expectations of -5° C to +25° C at an Altitude of 4,2000-m is easily accomplished. DFM's optical systems use Invar spacers to provide a nearly athermal optical support structure. Many situations have called for a mixture of Invar and steel to get a structure whose temperature coefficient of expansion is less than that of the Invar alone.

spot diagrams by wavelength
Spot Diagrams by Wavelength

Optical Performance Testing:
The optics are tested in DFM's Optical Shop in autocollimation and at varying gravity vectors. It requires a suitable equatorial fork mount to rotate the Optical Tube Assembly for accurate testing.

Optical Tube Assembly Collimation and Alignment:
The optics within the optical tube assembly on an equatorial fork mount exceeds basic standards of athermalization maintaining good collimation and alignment between -5° and +25° C for all elevations above 20°.

field corrector diagram
3 Element Field Corrector Diagram

Optical Tube Assembly Survey Speed:
The optical design provides images over a flat focal surface that deliver a net survey speed of 1.62 deg2/sec for a single Optical Tube Assembly using a single Type 1 camera. Optics are polished to a level where performance is much better than 60% of the ideal.

ATLAS Optics Specifications

ATLAS primary mirror
ATLAS Primary Mirror

•  All optics form an image of objects at infinity at temperatures between -5°C and +25°C.

•  The optical design includes a 1/4-inch thick filter in the beam.

•  A planar cryostat window determined by the field corrector element.

•  A 3/8-inch thick fused silica window for the cryostat allowing for a 5-mm distance between the cryostat window and the detector surface.

•  All reflective optics are enhanced coated having an average reflectance greater than 90% between 400 and 850 nm.

•  Maximum transmission of reflectance performance is achieved over a wide bandwidth and optimized for wavelengths from 240 nm to 2000nm.

•  A 3/8-inch thick fused silica window for the cryostat allowing for a 5-mm distance between the cryostat window and the detector surface.

For more information about the ATLAS Optical Tube Assembly (asteroid tracker) project and how to order an instrument for your institution, contact DFM Engineering.

 

•  ATLAS Optical Tube Assembly

•  ATLAS Specifications

•  Telescope Control Systems (TCSGalil™)

•  Equatorial Fork Mount

•  Telescope Optics

•  24" Cassegrain Telescope Features