insight - Scientific Computing - # Telescope Design

Optical Design and Implementation for the EXCLAIM Balloon-Borne Telescope

Q: How will the data collected by EXCLAIM be used to refine existing models of star formation and galaxy evolution?

EXCLAIM's unique approach to observing the universe will provide valuable data to refine models of star formation and galaxy evolution in several ways: Mapping the History of Star Formation: By observing the intensity of specific spectral lines ([CII] and CO) at different redshifts, EXCLAIM will effectively map the star formation rate density across cosmic time. This will provide a more complete picture of when and where star formation peaked and how it declined, offering insights into the underlying physical processes. Understanding the Role of Galactic Feedback: EXCLAIM's large-scale, unbiased survey will help disentangle the effects of galactic feedback mechanisms, such as supernovae and active galactic nuclei, which are thought to regulate star formation. By correlating the intensity maps with galaxy redshift surveys like BOSS, researchers can study how feedback processes vary with galaxy properties and environments. Constraining the CO-H2 Conversion Factor: The Galactic Plane survey of EXCLAIM will map both CO and [CI] emission. This will allow for a better calibration of the CO-H2 conversion factor, which is crucial for estimating the total molecular gas mass (a key ingredient for star formation) from CO observations. This calibration will improve the accuracy of star formation rate estimates not only for EXCLAIM but also for other studies relying on CO as a tracer. Testing Theoretical Models: The high-fidelity intensity maps produced by EXCLAIM will provide a stringent test for theoretical models of galaxy formation and evolution. By comparing model predictions with the observed distribution and evolution of star-forming gas, researchers can identify discrepancies and refine the models to better reflect the physical processes at play. Overall, EXCLAIM's data will provide a more comprehensive and unbiased view of star formation across cosmic time, allowing astronomers to refine existing models and gain a deeper understanding of how galaxies form and evolve.

Q: Could the optical design principles used in EXCLAIM be adapted for use in other types of telescopes or observational instruments, and if so, what fields of study might benefit?

Yes, several optical design principles employed in EXCLAIM hold potential for adaptation in other telescopes and instruments across various fields: Cryogenic Off-Axis Reflective Optics: The use of a completely cryogenic telescope with off-axis reflective optics minimizes thermal background noise, crucial for observing faint signals in the submillimeter and millimeter wavelengths. This design principle is beneficial for: Cosmic Microwave Background (CMB) studies: Observing faint polarization signals in the CMB to study the early universe. Far-infrared astronomy: Studying cold dust and gas in the interstellar medium, star-forming regions, and distant galaxies. Integrated Silicon Spectrometers (µ-Spec): The compact and highly sensitive nature of µ-Spec technology makes it suitable for: Multi-object spectroscopy: Simultaneously observing spectra from multiple astronomical objects, increasing observation efficiency. Compact and lightweight instruments: Enabling the development of smaller and more cost-effective instruments for deployment on CubeSats or other platforms. Stray Light Control: EXCLAIM's meticulous stray light control measures, including under-illumination of the primary mirror, blackened baffles, and strategic placement of filters, are valuable for: Exoplanet detection: Direct imaging and characterization of exoplanets, which requires suppressing the bright light from the host star. High-contrast imaging: Observing faint structures around bright objects, such as protoplanetary disks or active galactic nuclei. By adapting these design principles, future instruments can achieve higher sensitivity, broader bandwidth, and improved stray light rejection, enabling advancements in various fields like cosmology, astrophysics, and planetary science.

Q: Given the finite lifespan of balloon-borne observations, how might future space-based telescopes build upon the technological advancements and scientific discoveries of EXCLAIM to further our understanding of the universe?

While EXCLAIM's balloon-borne observations provide a crucial stepping stone, future space-based telescopes can capitalize on its technological advancements and scientific findings to push the boundaries of our understanding: Larger Apertures and Increased Sensitivity: Building upon EXCLAIM's cryogenic off-axis design, space telescopes can accommodate larger primary mirrors, enabling even higher sensitivity and angular resolution. This would allow for the detection of fainter and more distant sources, providing a more detailed view of the early universe and the processes governing galaxy formation. Wider Field of View and Survey Speed: Future missions can incorporate EXCLAIM's wide field of view and efficient mapping strategy to conduct larger and deeper surveys. This would enable the study of rarer objects and phenomena, providing statistically robust constraints on cosmological models and the evolution of the universe. Broader Spectral Coverage: Expanding upon EXCLAIM's frequency range, future space telescopes can observe a wider range of spectral lines, tracing different phases of the interstellar medium and providing a more complete picture of the cosmic baryon cycle. Improved Spectroscopic Resolution: Building on the success of EXCLAIM's µ-Spec technology, future instruments can achieve even higher spectral resolution. This would allow for detailed studies of the kinematics and chemical composition of distant galaxies, providing insights into the processes of star formation, feedback, and galaxy evolution. By combining these advancements with the scientific discoveries of EXCLAIM, future space-based telescopes like the Origins Space Telescope concept will be poised to revolutionize our understanding of the universe, from the first stars and galaxies to the intricate processes shaping the cosmos today.

Core Concepts

This paper details the design and implementation of the optics for EXCLAIM, a balloon-borne telescope designed to measure line emission from carbon monoxide and ionized carbon to study star formation across cosmic time.

Abstract

Bibliographic Information: Essinger-Hileman, T., Oxholm, T., Siebert, G., et al. (2024). Design and Implementation of Optics for the EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM). arXiv:2012.10481v2 [astro-ph.IM].
Research Objective: This paper describes the optical design and implementation of EXCLAIM, a balloon-borne telescope designed to measure integrated line emission from carbon monoxide (CO) at redshifts z < 1 and ionized carbon ([CII]) at redshifts z = 2.5 −3.5. The goal of EXCLAIM is to probe star formation over cosmic time by cross-correlating its observations with galaxy redshift surveys.
Methodology: The paper presents a detailed overview of the EXCLAIM optical design, including its off-axis Gregorian telescope layout, key components (mirrors, lenses, filters, baffles), and stray light control mechanisms. The authors use ray-tracing software (Zemax OpticStudio) and physical-optics analysis to model and validate the system's performance, ensuring it meets the stringent requirements for diffraction-limited imaging and minimal stray light contamination.
Key Findings: The EXCLAIM optical design successfully meets the demanding requirements for its scientific objectives. The system achieves a Strehl ratio greater than 0.80 across the entire field of view, ensuring high-quality imaging. The design effectively minimizes stray light contamination, with simulations demonstrating less than -40 dB of spill onto warm surfaces. The paper also details the manufacturing and alignment processes for the optical components, highlighting the precision achieved in their fabrication and assembly.
Main Conclusions: The authors successfully developed a sophisticated optical system for EXCLAIM that meets the stringent requirements for its mission. The design, validated through simulations and careful analysis, ensures diffraction-limited performance and effective stray light control. The paper provides a comprehensive overview of the optical system, highlighting its innovative features and the meticulous design and manufacturing processes involved.
Significance: The development of EXCLAIM and its advanced optical system represents a significant contribution to the field of astronomy. By enabling high-sensitivity measurements of CO and [CII] line emission, EXCLAIM will provide valuable insights into the processes of star formation across cosmic time. The success of this project paves the way for future balloon-borne and space-based telescopes with similarly demanding optical requirements.
Limitations and Future Research: While the paper thoroughly describes the current state of the EXCLAIM optical system, it acknowledges that further refinements and characterizations may be necessary. Future work could involve in-flight measurements and calibrations to optimize the system's performance and address any unforeseen issues that may arise during operation.

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Stats

The telescope will observe at frequencies of 420–540 GHz.
The telescope has a 90-cm primary mirror with a projected aperture of 76 cm.
The telescope has a 10-cm secondary mirror.
The telescope provides 4.2′ full-width at half-maximum (FWHM) resolution at the center of the EXCLAIM band over a field of view of 22.5′.
The system is cooled to a temperature below 5 K.
The instantaneous field of view (FOV) of the telescope is between 12.5′ and 25′.
The aluminum primary mirror has a measured RMS surface figure deviation of 12 µm within the inner 50 cm diameter.
The aluminum folding flat mirror has a measured RMS surface figure deviation of 6 µm.
The aluminum secondary mirror has a measured RMS surface figure deviation of 14 µm.

Quotes

Key Insights Distilled From

Optical Design of the EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM)

by Thomas Essin... at arxiv.org 11-06-2024

https://arxiv.org/pdf/2012.10481.pdf

Optical Design of the EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM)

Deeper Inquiries

How will the data collected by EXCLAIM be used to refine existing models of star formation and galaxy evolution?

EXCLAIM's unique approach to observing the universe will provide valuable data to refine models of star formation and galaxy evolution in several ways:

Mapping the History of Star Formation: By observing the intensity of specific spectral lines ([CII] and CO) at different redshifts, EXCLAIM will effectively map the star formation rate density across cosmic time. This will provide a more complete picture of when and where star formation peaked and how it declined, offering insights into the underlying physical processes.
Understanding the Role of Galactic Feedback: EXCLAIM's large-scale, unbiased survey will help disentangle the effects of galactic feedback mechanisms, such as supernovae and active galactic nuclei, which are thought to regulate star formation. By correlating the intensity maps with galaxy redshift surveys like BOSS, researchers can study how feedback processes vary with galaxy properties and environments.
Constraining the CO-H2 Conversion Factor:  The Galactic Plane survey of EXCLAIM will map both CO and [CI] emission. This will allow for a better calibration of the CO-H2 conversion factor, which is crucial for estimating the total molecular gas mass (a key ingredient for star formation) from CO observations. This calibration will improve the accuracy of star formation rate estimates not only for EXCLAIM but also for other studies relying on CO as a tracer.
Testing Theoretical Models: The high-fidelity intensity maps produced by EXCLAIM will provide a stringent test for theoretical models of galaxy formation and evolution. By comparing model predictions with the observed distribution and evolution of star-forming gas, researchers can identify discrepancies and refine the models to better reflect the physical processes at play.
Overall, EXCLAIM's data will provide a more comprehensive and unbiased view of star formation across cosmic time, allowing astronomers to refine existing models and gain a deeper understanding of how galaxies form and evolve.

Could the optical design principles used in EXCLAIM be adapted for use in other types of telescopes or observational instruments, and if so, what fields of study might benefit?

Yes, several optical design principles employed in EXCLAIM hold potential for adaptation in other telescopes and instruments across various fields:

Cryogenic Off-Axis Reflective Optics: The use of a completely cryogenic telescope with off-axis reflective optics minimizes thermal background noise, crucial for observing faint signals in the submillimeter and millimeter wavelengths. This design principle is beneficial for:

Cosmic Microwave Background (CMB) studies:  Observing faint polarization signals in the CMB to study the early universe.
Far-infrared astronomy: Studying cold dust and gas in the interstellar medium, star-forming regions, and distant galaxies.

Integrated Silicon Spectrometers (µ-Spec): The compact and highly sensitive nature of µ-Spec technology makes it suitable for:

Multi-object spectroscopy:  Simultaneously observing spectra from multiple astronomical objects, increasing observation efficiency.
Compact and lightweight instruments:  Enabling the development of smaller and more cost-effective instruments for deployment on CubeSats or other platforms.

Stray Light Control: EXCLAIM's meticulous stray light control measures, including under-illumination of the primary mirror, blackened baffles, and strategic placement of filters, are valuable for:

Exoplanet detection:  Direct imaging and characterization of exoplanets, which requires suppressing the bright light from the host star.
High-contrast imaging:  Observing faint structures around bright objects, such as protoplanetary disks or active galactic nuclei.
By adapting these design principles, future instruments can achieve higher sensitivity, broader bandwidth, and improved stray light rejection, enabling advancements in various fields like cosmology, astrophysics, and planetary science.

Given the finite lifespan of balloon-borne observations, how might future space-based telescopes build upon the technological advancements and scientific discoveries of EXCLAIM to further our understanding of the universe?

While EXCLAIM's balloon-borne observations provide a crucial stepping stone, future space-based telescopes can capitalize on its technological advancements and scientific findings to push the boundaries of our understanding:

Larger Apertures and Increased Sensitivity: Building upon EXCLAIM's cryogenic off-axis design, space telescopes can accommodate larger primary mirrors, enabling even higher sensitivity and angular resolution. This would allow for the detection of fainter and more distant sources, providing a more detailed view of the early universe and the processes governing galaxy formation.
Wider Field of View and Survey Speed:  Future missions can incorporate EXCLAIM's wide field of view and efficient mapping strategy to conduct larger and deeper surveys. This would enable the study of rarer objects and phenomena, providing statistically robust constraints on cosmological models and the evolution of the universe.
Broader Spectral Coverage: Expanding upon EXCLAIM's frequency range, future space telescopes can observe a wider range of spectral lines, tracing different phases of the interstellar medium and providing a more complete picture of the cosmic baryon cycle.
Improved Spectroscopic Resolution: Building on the success of EXCLAIM's µ-Spec technology, future instruments can achieve even higher spectral resolution. This would allow for detailed studies of the kinematics and chemical composition of distant galaxies, providing insights into the processes of star formation, feedback, and galaxy evolution.
By combining these advancements with the scientific discoveries of EXCLAIM, future space-based telescopes like the Origins Space Telescope concept will be poised to revolutionize our understanding of the universe, from the first stars and galaxies to the intricate processes shaping the cosmos today.