Infrared Telescope Requirement_REVISED.docx

Statement of Work Infrared Telescope

I. Background Science objective:

NIST is working on a project that requires an infrared telescope system to make accurate spectral irradiance measurements of the light from standard stars in the wavelength range between 850 nm and 2500 nm. Observations will be made at high altitude above 2600 m (8600 feet) in dry (low precipitable water vapor) environments to maximize access to clear skies and minimize telluric effects (e.g., aerosols). These measurements will then serve as standard calibration spectra for multiple stakeholders who operate other astronomical instruments and satellite instruments.

Telescope installation is expected in 2023.

Operational objective:

The operational objective is accurate spectral irradiance measurements of real stars in the sky relative to an artificial star (the absolute radiometric standard) on the ground. Therefore, the telescope system required in this procurement is best thought of as a light bucket: it must provide an image of the source focused onto the input face of a 600-micrometer core diameter optical fiber, which subsequently feeds the light into a spectrometer. The optical fiber’s numerical aperture is greater than that associated with the telescope, so that the telescope entrance aperture defines the entrance pupil diameter of the system. Radiometric calibration of the telescope will be performed by the user in the field, using a 1-mm diameter artificial star placed at 100 m from the entrance aperture of the telescope. It is anticipated that the image position at the back of the telescope will shift about 2.5 inches depending on whether the imaged object is the real star (at infinity) or the (user-provided) artificial star (at 100 m). This shift will be accommodated by a focuser provided by the user as described below. Image quality is important only for the on-axis source, and only to the degree that it affects the encircled energy function. To enable alignment and tracking, a beam splitter located between the telescope output and fiber input sends visible light to a dedicated guider camera. The beam splitter, guider camera, focuser, and optical fiber together comprise a separate user-provided component of the optical system, called the “optical cross”, which is user-mounted behind the telescope. The optical cross hardware itself and the fiber-coupled spectrometer are not part of this equipment acquisition. However, an interface plate to the optical cross must be provided on the back of the telescope, and this interface plate is part of the procurement as it is part of the telescope mechanical structure. The design of this optical cross interface plate and internal baffling structures must permit the installation and use of a focuser (part of the optical cross) having a travel of at least 2.5 inches (or as required to accommodate the focus shift between standard star at infinity and artificial star at 100 m), with no vignetting of rays at the extremum of the travel.

The telescope operating site will be on Cerro Paranal, Chile. During nighttime operation, the telescope will be completely exposed to the outside. Calibration measurements will be made at regular intervals during the night, alternating with exposures of the stars. Measurements of the sky are obtained between star exposures. When not in use, the telescope is protected from the environment by an enclosure.

Typical Operational conditions at Cerro Paranal, Chile

On occasion can reach 40C

II. Scope of Work This equipment acquisition is for an infrared sensitive telescope and associated mount to be located at a high-altitude astronomical observatory on Cerro Paranal in Chile (2635 m altitude). The user must be able to point to and track stars from star rise to star set and to point to an artificial star located approximately 100 m away from the telescope. Because the artificial star may be located 10 degrees below the horizon, the telescope must be capable of pointing to the zenith and to a sub-horizon point and be mechanically stable throughout the range of motion.

III. Minimum Requirements The system shall meet or exceed the minimum requirements identified below. All items must be new. Used or remanufactured equipment will not be considered for award. Experimental, prototype, or custom items will not be considered. The use of “gray market” components not authorized for sale in the U.S. by the proposer is not acceptable. All line items shall be shipped in the original manufacturer’s packaging and include all original documentation and software, when applicable.

The Contractor shall provide a telescope system that meets the following:

Contract Line Item Number (CLIN) 0001: The Contractor shall provide Optical Telescope Assembly Requirements as follows:

A.1 The telescope design shall be optimized for radiometry and spectroscopy, i.e. light from an artificial star at 100 m or from a natural star is delivered into an on-axis optical fiber, which in turn feeds light into a spectrograph.

1a. The optical design (e.g., Ritchey-Chretien, Dahl-Kirkham etc.) is unconstrained. The objective is on-axis stellar spectroscopy. Optimizing imaging quality over a wide field of view is not necessary.

1b. Focusing position changes between natural star and artificial star will be accommodated by a user-provided focusing assembly that is part of a user-provided Optical Cross (see A.15). Therefore, the telescope itself need not have any Contractor-provided moveable parts to accommodate the focus change between the artificial star and natural stars.

1c. The optical telescope assembly shall interface with the Optical Cross. (see A.15) A.2 The telescope design shall be optimized for astronomical spectroscopic measurements between 850 nm and 2500 nm and meet optical requirements at 1800 nm.

A.3 The primary mirror nominal diameter shall be 490 mm (20 inches).

3a. The primary mirror diameter shall be larger than 416 mm, with preference for a size that is standard for the Contractor.

3b. The central hole diameter is determined by the need to not clip light in the presence of baffles from either an artificial or natural star.

A.4 The maximum (linear) obscuration (ratio of secondary mirror diameter to primary mirror diameter) shall not exceed 40%.

A.5 The mirror surface roughness shall be less than 2 nm RMS (root mean square) or industry standard for reflecting telescopes at visible wavelengths.

A.6 The mirror base shall be from zerodur or and equivalent material.

A.7 The optical telescope assembly shall be stable at the expected operating temperature and humidity on Cerro Paranal:

7a. Operating temperature between -10 and 40 degrees C.

7b. Operating humidity between 0% Relative Humidity (RH) and 20% RH.

A.8 The telescope mirrors shall meet storage temperature requirements: between -10 and +60 degrees C A.9 While the optical fiber is not provided by the Contractor, the telescope design shall be compatible with the optical fiber in the following manner: The telescope shall have an f/# such that rays are not clipped on the receiving surface of the optical fiber. The NIST-provided optical fiber will be located at the output of the optical cross (see A. 15), has a core diameter of 600 micrometers, and has a Numerical Aperture (NA) of 0.22.

A.10 The telescope shall have an entrance aperture that defines the entrance pupil at a definite, planar location at the front of the telescope. This defining aperture shall have a knife-like edge to define the beam cross section. The knife edge shall have a land that is minimally practical within the machining limitations, and the aperture shall be beveled on the side facing the telescope interior. The aperture shall provide a shadow margin no smaller than 4 mm from the primary perimeter, central obscuration, and central obscuration supports. (As a result, all incident light from a star shall only be incident on the entrance aperture and primary.)

10a. Locations of the primary perimeter, central obscuration, and central obscuration supports shall be knowable, so that one can determine definite distance between the telescope entrance aperture and the exit aperture of the artificial star to 10 cm over 100 meters 10b. The defining aperture should be field-replaceable by the user. The surface of the defining aperture that faces inward to the telescope shall have a diffuse-black coating like the baffles in order to capture stray light.

10c. A schematic figure of an entrance aperture is shown in Section VI A.11 The change in throughput into a 600-micrometer core diameter optical fiber due to a 10 arcsec change of angle shall be no more than 0.2%.

A.12 Stray Light. Control of stray light is critical for radiometry. Stray light requirements are:

12a. No more than 0.01% of the total light entering the fiber shall be light from points or angles outside the field of view. The baffle design must such that when back-illuminating the fiber, 99.99% of the total light seen by the virtual detector comes from within the field of view. For example, the baffles should block annular rings of light such as could be generated by light scattering of interior walls.

12b. The Contractor shall provide their optical design to NIST to enable for independent analysis that it meets the stray light requirement.

A.13 The optical tube assembly shall include the mechanical supports for the primary mirror and primary mirror cell, the secondary mirror, secondary mirror vanes, baffles, entrance aperture, interface plate for the optical cross and focuser to be supplied by NIST (see Req. A.15).

A.14 The Contractor shall provide a user-removable/replaceable primary mirror cover.

A.15 Interface to NIST-supplied Optical Cross and Focuser:

15a. This paragraph is provided to help the Contractor understand the purpose of the NIST-supplied Optical Cross and Focuser. The Optical Cross is centered around a beam splitter that directs most of the beam to the optical fiber and a small fraction to a camera. This enables the camera to view the star for tracking purposes. The Focuser moves the Optical Cross along the optical axis to accommodate the large focus position shift between the natural star and the artificial star. It also enables fine focus to adjust to ensure that the optical fiber input tip remains in focus. A second camera that is part of the optical cross is used to visualize the focused spot at the input face of the optical fiber.

15b. The Contractor shall provide an Interface Plate fixed at the rear of the telescope to enable NIST to mount the NIST-provided Optical Cross and Focuser. This interface plate shall have a grid of ¼-20 tapped mounting holes on 1-inch spacing and include a hole for allowing the optical beam to pass through. The normal to the interface plate shall be parallel to the telescope optical axis. The thickness of the interface plate shall be at least 0.375 inches. The NIST-provided Optical Cross will be bolted into the mounting holes. Physical dimensions, weight, and mechanical details of the Optical Cross will be provided by NIST. Optical properties of the beam splitter will also be provided by NIST.

15c. The back working distance of the telescope, defined as the distance along the optical axis between the back surface of the Interface Plate and the location of the telescope focus for an object at infinity, shall be at least 123 millimeters.

15d. The Contractor shall estimate the difference in focal position along the optical axis for natural star vs. artificial star during the design phase, and this shall be communicated to NIST during the design so that NIST can design the Focuser to accommodate.

A.16 The top-level optical performance requirements of the telescope system are:

16a. At the focus for a point source (natural star at infinity), the encircled energy of the image within a 600-micrometer diameter circle in the focal plane normal to the optical axis shall contain at least 98.5 % of the total energy at that plane, at a wavelength of 1800 nm.

16b. At the focus for a 1-mm diameter uniform source placed 100 m from the entrance aperture of the telescope (artificial star), the encircled energy of the image within a 600-micrometer diameter circle in the focal plane normal to the optical axis shall contain at least 98.5 % of the total energy at that plane, at a wavelength of 1800 nm.

16c. When properly focused for each of the two sources defined above, the change of encircled energy within a 600-micrometer diameter circle in the focal plane normal to the optical axis shall be less than 0.15 % at a wavelength of 1800 nm.

16d. These optical requirements apply to the full system, comprised of the Contractor-provided telescope optics and the NIST-provided beam splitter that is part of the Optical Cross. The optical prescription of the optical cross beam splitter will be provided by NIST during the Contractor design process.

16e. NIST will provide the Contractor with the design for mounting the Optical Cross and Focuser. The mechanical design must allow for sufficient space behind the primary mirror cell to locate the optical cross assembly (see A.15). This space must be easily accessible and without mechanical interference from other components.

A.17 The Contractor shall provide NIST prior to hardware build, predictions for the change of encircled energy for a point source at infinity and an artificial star at 100 m when the telescope is properly focused, for 12 wavelengths evenly spaced between and including 850 nm and 2500 nm. Analysis must be supported by a full optical chain prescription, including all parts that affect light propagation.

CLIN 0002: The Contractor shall provide Mount Requirements as follows:

A.18 The Contractor shall provide equatorial mount for the latitude at Cerro Paranal in Chile,

24.6272 degrees South. A fork mount is preferred.

A.19 The Mount must support the Optical Telescope Assembly described in Part A, along with the weight of the Optical Cross and Focuser. The mass of the NIST-provided Optical Cross is estimated at 5.5 kg.

A.20 The Contractor shall provide minimum bend radius that would be induced in a fiber run through the Mount.

CLIN 003: The Contractor shall provide Motion Control Requirements as follows:

A.21 The telescope shall point 10 degrees below the horizon, and to and through the zenith without mechanical deformation or changes that affect the above specifications in Section A.

A.22 The motion control shall provide pointing and tracking accuracy capability as follows:

22a. Pointing accuracy: ≤10 arcsec root-mean-square (RMS) 22b. Tracking accuracy: < 0.1 arcsec during a 30 second period A.23 The motion control shall provide motion range to allow sky coverage as follows:

23a. Altitude Range: -10 to 90 degrees 23b. Azimuth Range: +/- 360 degrees A.24 The Contractor shall provide a software interface to telescope control software via e.g., an Application Programming Interface (API).

A.25 The Contractor’s software shall allow system state metadata to be accessible to the user.

A.26 The Contractor’s software shall allow the user to specify telescope pointing to objects below the horizon (for calibration by viewing the artificial star).

A.27 The Contractor’s software shall allow user to point telescope to any specified objects with the option of no refraction correction (e.g., objects near the horizon).

A.28 The Contractor shall provide an alignment/collimation kit.

CLIN 0004: The Contractor shall provide training on installation for CLINs 0001 – 0003 in accordance with the following:

NIST will prepare the telescope site on Cerro Paranal in Chile; this includes the concrete telescope pad and pier for placing the mount, and the telescope enclosure. Details of the pier-to-mount interface will be discussed with Contractor at telescope design review. The Contractor will ship the optical telescope assembly (OTA) to NIST in Gaithersburg for calibration. NIST will be responsible for then shipping the telescope to Cerro Paranal, Chile and for its installation on the site. Contractor shall provide training for NIST personnel see Section VII).

IV. Delivery Contractor shall deliver turn-key telescope system, operation manual(s), software manual(s), electrical/mechanical manual(s) as specified by NIST. T0 is the date on which OTA arrives at NIST in MD. Estimated completion dates are relative.

Telescope arrives at NIST, MD

T0

Delivery shall be FOB DESTINATION.

FOB Destination means: The contractor shall pack the system in the shipping containers and mark the shipment in conformance with carrier requirements, deliver the shipment in good order and condition to the point of delivery specified in the purchase order, be responsible for any loss of and/or damage to the goods occurring before receipt and acceptance of the shipment by the consignee at the delivery point specified in the purchase order; and pay all charges to the specified point of delivery. The telescope system will be shipped in a dedicated, reusable case(s) for air transport and shipment. Case must have wheels.

The contractor shall deliver all Line Items to:

National Institute of Standards and Technology 100 Bureau Drive, Building 217, Room A243 Gaithersburg, MD 20899-1640, United States of America

V. Inspection and Acceptance NIST COR or TPOC may visit Contractor’s site at final assembly and checkout before shipping NIST In addition to the inspection and acceptance terms articulated above and inspection and acceptance done at the Contractor’s facility during training, the Government reserves the right to perform such performance tests and evaluations as defined below to verify specified system performance. Such tests and evaluations, if performed, shall be conducted within the environment that the system is to be operated. The Contractor has the right to be present during the tests and evaluations, if performed, at the Contractor’s expense.

1) The Government will test, inspect, and accept optics design within 15 business days of the receipt of a Zemax-compatible file

2) Contractor shall provide NIST’s Contracting Officer Representative and Technical Point of Contact the optics design. NIST will check that radiometric specifications meet or exceed requirements for RMS Spot diagram, encircled energy, and stray light

3) The Government will test, inspect, and accept the equipment onsite within 19 Calendar Days of the receipt of the telescope, i.e. mirrors, baffles etc., mounted in the ‘tube’ or ‘truss’.

4) During the performance testing at NIST, the Telescope will be operated and checked to be in compliance with the specifications for optical performance. Data will be collected and analyzed to ensure performance is within specifications.

A visual inspection of the system will be performed by the NIST TPOC to identify surface defects or any form of indication that the system was damaged during transport to NIST. The Government shall have sole discretion to require repair or replacement of damaged and/or nonconforming supplies at no cost to the Government. The Government at any time prior to acceptance shall reject the system due to defects and/or nonconformance.

VI. Government-Furnished Property, Material, Equipment, or Information (GFP, GFM, GFE, or GFI)

1. Schematic of an entrance aperture, specified in Requirement A.10.

2. The Government shall provide the focusing system, known as the optical cross. NIST shall provide the Contractor with dimensional information and design schematic of the optical cross.

3. Example of a 2-mirror design used by the Government in a related study is provided here:

VII. Training Contractor shall conduct at Contractor’s location, training session for up to 4 NIST personnel on installation, alignment, and operation of the telescope system. The training shall provide a thorough demonstration of all system/solution functions, maintenance, data administration, and basic troubleshooting. Contractor will be available to NIST personnel during installation of telescope system via telephone and email.

VIII. Warranty The Contractor shall provide a warranty in accordance with commercial practices and in accordance with 52.212-4.

IX. Payment Schedule The Contractor shall be paid, in accordance with Net 30-day payment terms, upon receipt and acceptance of a proper invoice, in accordance with the following schedule:

1. CLIN 001: A 30% milestone payment will be made after NIST approval of the design, with remaining 70% paid after delivery of OTA to NIST,

2. CLIN 002 & CLIN 003. Payment in full within 14 days after delivery (received at NIST)

3. CLIN 004: Payment in full within 7 days after installation on the site at Paranal.

4. The Government anticipates inspection will occur upon final delivery after the testing procedures set forth in this document have been completed.

NOTE: Partial shipments/installation and partial invoices will not be accepted, unless otherwise requested and accepted by the Contracting Officer prior to award offer. Proposed payment schedules shall be submitted with Contractor’s response to the RFQ for consideration.

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