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The Simons Observatory (SO) will be a cosmic microwave background (CMB) survey experiment with three small-aperture telescopes (SATs) and one large-aperture telescope (LAT), which will observe from the Atacama Desert in Chile. In total, SO will field over 60,000 transition-edge sensor (TES) bolometers in six spectral bands centered between 27 and 280 GHz in order to achieve the sensitivity necessary to measure or constrain numerous cosmological quantities. The SATs are optimized for a primordial gravitational wave signal in a parity odd polarization power spectrum at a large angular scale. We will present the latest status of the SAT development.
The Simons Observatory (SO) will be a cosmic microwave background (CMB) survey experiment with three small-aperture telescopes (SATs) and one large-aperture telescope, which will observe from the Atacama Desert in Chile. To control for systematics in the polarization signal, the SAT design will use a continuously rotating cryogenic half wave plate (HWP) on a high-temperature superconductor magnetic levitation bearing. This is the largest such cryogenic rotation mechanism to be deployed on a telescope to date. We will discuss the design and the mechanical and thermal performance of the SAT HWP rotator.
The BLAST Observatory is a proposed super-pressure balloon-borne polarimeter designed for a future ultra- long duration balloon campaign from Wanaka, New Zealand. To maximize scientific output while staying within the stringent super-pressure weight envelope, BLAST will feature new 1.8m off-axis optical system contained within a lightweight monocoque structure gondola. The payload will incorporate a 300 L 4He cryogenic receiver which will cool 8,274 microwave kinetic inductance detectors (MKIDs) to 100mK through the use of an adiabatic demagnetization refrigerator (ADR) in combination with a 3He sorption refrigerator all backed by a liquid helium pumped pot operating at 2 K. The detector readout utilizes a new Xilinx RFSOC-based system which will run the next-generation of the BLAST-TNG KIDPy software. With this instrument we aim to answer outstanding questions about dust dynamics as well as provide community access to the polarized submillimeter sky made possible by high-altitude observing unrestricted by atmospheric transmission. The BLAST Observatory is designed for a minimum 31-day flight of which 70% will be dedicated to observations for BLAST scientific goals and the remaining 30% will be open to proposals from the wider astronomical community through a shared-risk proposals program.
The Next Generation Balloon-Borne Large Aperture Submillimeter Telescope (BLAST-TNG) was a unique instrument for characterizing the polarized submillimeter sky at high-angular resolution. BLAST-TNG flew from the Long Duration Balloon Facility in Antarctica in January 2020. Despite the short flight duration, the instrument worked very well and is providing significant information about each subsystem that will be invaluable for future balloon missions. In this contribution, we discuss the performance of telescope and gondola.
The Next Generation Balloon-borne Large Aperture Submillimeter Telescope (BLAST-TNG) is a submillimeter polarimeter designed to map interstellar dust and galactic foregrounds at 250, 350, and 500 microns during a 24-day Antarctic flight. The BLAST-TNG detector arrays are comprised of 918, 469, and 272 MKID pixels, respectively. The pixels are formed from two orthogonally oriented, crossed, linear-polarization sensitive MKID antennae. The arrays are cooled to sub 300 mK temperatures and stabilized via a closed cycle 3He sorption fridge in combination with a 4He vacuum pot. The detectors are read out through a combination of the second-generation Reconfigurable Open Architecture Computing Hardware (ROACH2) and custom RF electronics designed for BLAST-TNG. The firmware and software designed to readout and characterize these detectors was built from scratch by the BLAST team around these detectors, and has been adapted for use by other MKID instruments such as TolTEC and OLIMPO.1 We present an overview of these systems as well as in-depth methodology of the ground-based characterization and the measured in-flight performance.
The Simons Observatory (SO) will make precision temperature and polarization measurements of the cosmic
microwave background (CMB) using a series of telescopes which will cover angular scales between 1 arcminute
and tens of degrees, contain over 40,000 detectors, and sample frequencies between 27 and 270 GHz. SO will
consist of a six-meter-aperture telescope coupled to over 20,000 detectors along with an array of half-meter
aperture refractive cameras, coupled to an additional 20,000+ detectors. The unique combination of large and
small apertures in a single CMB observatory, which will be located in the Atacama Desert at an altitude of
5190 m, will allow us to sample a wide range of angular scales over a common survey area. SO will measure
fundamental cosmological parameters of our universe, find high redshift clusters via the Sunyaev-Zeldovich effect,
constrain properties of neutrinos, and seek signatures of dark matter through gravitational lensing. The complex
set of technical and science requirements for this experiment has led to innovative instrumentation solutions
which we will discuss. The large aperture telescope will couple to a cryogenic receiver that is 2.4 m in diameter
and over 2 m long, creating a number of interesting technical challenges. Concurrently, we are designing an array
of half-meter-aperture cryogenic cameras which also have compelling design challenges. We will give an overview
of the drivers for and designs of the SO telescopes and the cryogenic cameras that will house the cold optical
components and detector arrays.
The Simons Observatory (SO) will observe the temperature and polarization anisotropies of the cosmic microwave background (CMB) over a wide range of frequencies (27 to 270 GHz) and angular scales by using both small (∼0.5 m) and large (∼6 m) aperture telescopes. The SO small aperture telescopes will target degree angular scales where the primordial B-mode polarization signal is expected to peak. The incoming polarization signal of the small aperture telescopes will be modulated by a cryogenic, continuously-rotating half-wave plate (CRHWP) to mitigate systematic effects arising from slowly varying noise and detector pair-differencing. In this paper, we present an assessment of some systematic effects arising from using a CRHWP in the SO small aperture systems. We focus on systematic effects associated with structural properties of the HWP and effects arising when operating a HWP, including the amplitude of the HWP synchronous signal (HWPSS), and I → P (intensity to polarization) leakage that arises from detector non-linearity in the presence of a large HWPSS. We demonstrate our ability to simulate the impact of the aforementioned systematic effects in the time domain. This important step will inform mitigation strategies and design decisions to ensure that SO will meet its science goals.
POLARBEAR-2 is a new receiver system, which will be deployed on the Simons Array telescope platform, for the measurement of Cosmic Microwave Background (CMB) polarization. The science goals with POLARBEAR-2 are to characterize the B-mode signal both at degree and sub-degree angular-scales. The degree-scale polarization data can be used for quantitative studies on inflation, such as the reconstruction of the energy scale of inflation. The sub-degree polarization data is an excellent tracer of large-scale structure in the universe, and will lead to precise constraints on the sum of the neutrino masses. In order to achieve these goals, POLARBEAR-2 employs 7588 polarization-sensitive antenna-coupled transition-edge sensor (TES) bolometers on the focal plane cooled to 0.27K with a three-stage Helium sorption refrigerator, which is ~6 times larger array over the current receiver system. The large TES bolometer array is read-out by an upgraded digital frequency-domain multiplexing system capable of multiplexing 40 bolometers through a single superconducting quantum interference device (SQUID).
The first POLARBEAR-2 receiver, POLARBEAR-2A is constructed and the end-to-end testing to evaluate the integrated performance of detector, readout, and optics system is being conducted in the laboratory with various types of test equipments. The POLARBEAR-2A is scheduled to be deployed in 2018 at the Atacama desert in Chile. To further increase measurement sensitivity, two more POLARBEAR-2 type receivers will be deployed soon after the deployment (Simons Array project). The Simons Array will cover four frequency bands at 95GHz, 150GHz, 220GH and 270GHz for better control of the foreground signal. The projected constraints on a tensor-to-scalar ratio (amplitude of inflationary B-mode signal) is σ(r=0.1) = $6.0 \times 10^{-3}$ after foreground removal ($4.0 \times 10^{-3}$ (stat.)), and the sensitivity to the sum of the neutrino masses when combined with DESI spectroscopic galaxy survey data is 40 meV at 1-sigma after foreground removal (19 meV(stat.)).
We will present an overview of the design, assembly and status of the laboratory testing of the POLARBEAR-2A receiver system as well as the Simons Array project overview.
POLARBEAR is a cosmic microwave background (CMB) polarization experiment located in the Atacama desert in Chile. The science goals of the POLARBEAR project are to do a deep search for CMB B-mode polarization created by inflationary gravitational waves, as well as characterize the CMB B-mode signal from gravitational lensing. POLARBEAR-1 started observations in 2012, and the POLARBEAR team has published a series of results from its first two seasons of observations, including the first measurement of a non-zero B-mode polarization angular power spectrum, measured at sub-degree scales where the dominant signal is gravitational lensing of the CMB. The Simons Array expands POLARBEAR to include an additional two telescopes with next-generation POLARBEAR-2 multi-chroic receivers, observing at 95, 150, 220, and 270 GHz.
The POLARBEAR-2A focal plane has 7,588 transition-edge sensor bolometers, read out with frequency-division multiplexing, with 40 frequency channels within the readout bandwidth of 1.5 to 4.5 MHz. The frequency channels are defined by a low-loss lithographed aluminum spiral inductor and interdigitated capacitor in series with each bolometer, creating a resonant frequency for each channel's unique voltage bias and current readout. Characterization of the readout includes measuring resonant peak locations and heights and fitting to a circuit model both above and below the bolometer superconducting transition temperature. This information is used determine the optimal detector bias frequencies and characterize stray impedances which may affect bolometer operation and stability. The detector electrical characterization includes measurements of the transition properties by sweeping in temperature and in voltage bias, measurements of the bolometer saturation power, as well as measuring and removing any biases introduced by the readout circuit. We present results from the characterization, tuning, and operation of the fully integrated focal plane and readout for the first POLARBEAR-2 receiver, POLARBEAR-2A, during its pre-deployment integration run.
The Simons Observatory (SO) is an upcoming experiment that will study temperature and polarization fluctuations in the cosmic microwave background (CMB) from the Atacama Desert in Chile. SO will field both a large aperture telescope (LAT) and an array of small aperture telescopes (SATs) that will observe in six bands with center frequencies spanning from 27 to 270 GHz. Key considerations during the SO design phase are vast, including the number of cameras per telescope, focal plane magnification and pixel density, in-band optical power and camera throughput, detector parameter tolerances, and scan strategy optimization. To inform the SO design in a rapid, organized, and traceable manner, we have created a Python-based sensitivity calculator with several state-of-the-art features, including detector-to-detector optical white-noise correlations, a handling of simulated and measured bandpasses, and propagation of low-level parameter uncertainties to uncertainty in on-sky noise performance. We discuss the mathematics of the sensitivity calculation, the calculator's object-oriented structure and key features, how it has informed the design of SO, and how it can enhance instrument design in the broader CMB community, particularly for CMB-S4.
The Simons Observatory (SO) will make precision temperature and polarization measurements of the cosmic microwave background (CMB) using a series of telescopes which will cover angular scales between one arcminute and tens of degrees, contain over 60,000 detectors, and sample frequencies between 27 and 270 GHz. SO will consist of a six-meter-aperture telescope coupled to over 30,000 detectors along with an array of half-meter aperture refractive cameras, which together couple to an additional 30,000+ detectors. SO will measure fundamental cosmological parameters of our universe, find high redshift clusters via the Sunyaev-Zeldovich effect, constrain properties of neutrinos, and seek signatures of dark matter through gravitational lensing. In this paper we will present results of the simulations of the SO large aperture telescope receiver (LATR). We will show details of simulations performed to ensure the structural integrity and thermal performance of our receiver, as well as will present the results of finite element analyses (FEA) of designs for the structural support system. Additionally, a full thermal model for the LATR will be described. The model will be used to ensure we meet our design requirements. Finally, we will present the results of FEA used to identify the primary vibrational modes, and planned methods for suppressing these modes. Design solutions to each of these problems that have been informed by simulation will be presented.
The Simons Observatory (SO) will make precision temperature and polarization measurements of the cosmic microwave background (CMB) using a series of telescopes which will cover angular scales between one arcminute and tens of degrees and sample frequencies between 27 and 270 GHz. Here we present the current design of the large aperture telescope receiver (LATR), a 2.4m diameter cryostat that will be mounted on the SO 6m telescope and will be the largest CMB receiver to date. The cryostat size was chosen to take advantage of the large focal plane area having high Strehl ratios, which is inherent to the Cross-Dragone telescope design. The LATR will be able to accommodate thirteen optics tubes, each having a 36 cm diameter aperture and illuminating several thousand transition-edge sensor (TES) bolometers. This set of equipment will provide an opportunity to make measurements with unparalleled sensitivity. However, the size and complexity of the LATR also pose numerous technical challenges. In the following paper, we present the design of the LATR and include how we address these challenges. The solutions we develop in the process of designing the LATR will be informative for the general CMB community, and for future CMB experiments like CMB-S4.
The Next Generation Balloon-borne Large Aperture Submillimeter Telescope (BLAST-TNG) is a submillimeter mapping experiment planned for a 28 day long-duration balloon (LDB) flight from McMurdo Station, Antarctica during the 2018-2019 season. BLAST-TNG will detect submillimeter polarized interstellar dust emission, tracing magnetic fields in galactic molecular clouds. BLAST-TNG will be the first polarimeter with the sensitivity and resolution to probe the ~0.1 parsec-scale features that are critical to understanding the origin of structures in the interstellar medium.
BLAST-TNG features three detector arrays operating at wavelengths of 250, 350, and 500 m (1200, 857, and 600 GHz) comprised of 918, 469, and 272 dual-polarization pixels, respectively. Each pixel is made up of two crossed microwave kinetic inductance detectors (MKIDs). These arrays are cooled to 275 mK in a cryogenic receiver. Each MKID has a different resonant frequency, allowing hundreds of resonators to be read out on a single transmission line. This inherent ability to be frequency-domain multiplexed simplifies the cryogenic readout hardware, but requires careful optical testing to map out the physical location of each resonator on the focal plane. Receiver-level optical testing was carried out using both a cryogenic source mounted to a movable xy-stage with a shutter, and a beam-filling, heated blackbody source able to provide a 10-50 C temperature chop. The focal plane array noise properties, responsivity, polarization efficiency, instrumental polarization were measured. We present the preflight characterization of the BLAST-TNG cryogenic system and array-level optical testing of the MKID detector arrays in the flight receiver.
The Simons Observatory will consist of a single large (6 m diameter) telescope and a number of smaller (∼0.5 m diameter) refracting telescopes designed to measure the polarization of the Cosmic Microwave Background to unprecedented accuracy. The large aperture telescope is the same design as the CCAT-prime telescope, a modified Crossed Dragone design with a field-of-view of over 7.8 degrees diameter at 90 GHz. This paper presents an overview of the cold reimaging optics for this telescope and what drove our choice of 350–400 mm diameter silicon lenses in a 2.4 m cryostat over other possibilities. We will also consider the future expandability of this design to CMB Stage-4 and beyond.
The Next Generation Balloon-borne Large Aperture Submillimeter Telescope (BLAST-TNG) is a submillimeter mapping experiment planned for a 28 day long-duration balloon (LDB) flight from McMurdo Station, Antarctica during the 2018-2019 season. BLAST-TNG will detect submillimeter polarized interstellar dust emission, tracing magnetic fields in galactic molecular clouds. BLAST-TNG will be the first polarimeter with the sensitivity and resolution to probe the ∼0.1 parsec-scale features that are critical to understanding the origin of structures in the interstellar medium. With three detector arrays operating at 250, 350, and 500 μm (1200, 857, and 600 GHz), BLAST-TNG will obtain diffraction-limited resolution at each waveband of 30, 41, and 59 arcseconds respectively. To achieve the submillimeter resolution necessary for its science goals, the BLAST-TNG telescope features a 2.5 m aperture carbon fiber composite primary mirror, one of the largest mirrors flown on a balloon platform. Successful performance of such a large telescope on a balloon-borne platform requires stiff, lightweight optical components and mounting structures. Through a combination of optical metrology and finite element modeling of thermal and mechanical stresses on both the telescope optics and mounting structures, we expect diffractionlimited resolution at all our wavebands. We expect pointing errors due to deformation of the telescope mount to be negligible. We have developed a detailed thermal model of the sun shielding, gondola, and optical components to optimize our observing strategy and increase the stability of the telescope over the flight. We present preflight characterization of the telescope and its platform.
Polarized thermal emission from interstellar dust grains can be used to map magnetic fields in star forming molecular clouds and the diffuse interstellar medium (ISM). The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol) flew from Antarctica in 2010 and 2012 and produced degree-scale polarization maps of several nearby molecular clouds with arcminute resolution. The success of BLASTPol has motivated a next-generation instrument, BLAST-TNG, which will use more than 3000 linear polarization- sensitive microwave kinetic inductance detectors (MKIDs) combined with a 2.5 m diameter carbon fiber primary mirror to make diffraction-limited observations at 250, 350, and 500 µm. With 16 times the mapping speed of BLASTPol, sub-arcminute resolution, and a longer flight time, BLAST-TNG will be able to examine nearby molecular clouds and the diffuse galactic dust polarization spectrum in unprecedented detail. The 250 μm detec- tor array has been integrated into the new cryogenic receiver, and is undergoing testing to establish the optical and polarization characteristics of the instrument. BLAST-TNG will demonstrate the effectiveness of kilo-pixel MKID arrays for applications in submillimeter astronomy. BLAST-TNG is scheduled to fly from Antarctica in December 2017 for 28 days and will be the first balloon-borne telescope to offer a quarter of the flight for “shared risk” observing by the community.
The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol) is a suborbital mapping experiment designed to study the role magnetic fields play in star formation. BLASTPol has had two science flights from McMurdo Station, Antarctica in 2010 and 2012. These flights have produced thousands of polarization vectors at 250, 350 and 500 microns in several molecular cloud targets. We present the design, specifications, and progress towards the next-generation BLASTPol experiment (BLAST-TNG). BLAST-TNG will fly a 40% larger diameter primary mirror, with almost 8 times the number of polarization-sensitive detectors resulting in a factor of 16 increase in mapping speed. With a spatial resolution of 2200 and four times the field of view (340 arcmin2) of BLASTPol, BLAST-TNG will bridge the angular scales between Planck's all-sky maps with 50 resolution and ALMA's ultra-high resolution narrow (~ 2000) fields. The new receiver has a larger cryogenics volume, allowing for a 28 day hold time. BLAST-TNG employs three arrays of Microwave Kinetic Inductance Detectors (MKIDs) with 30% fractional bandwidth at 250, 350 and 500 microns. In this paper, we will present the new BLAST-TNG instrument and science objectives.
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