arXiv subjects

Ian N. Lowe

Publications and source records attributed to Ian N. Lowe.

4 recordsLinked to original sources

arXiv2026

TIME Commissioning Observations: II. On-sky Characterization and the 2D Map Data Processing Pipeline

The Tomographic Ionized-carbon Mapping Experiment (TIME) is a line intensity mapping (LIM) instrument that is designed to observe the power spectrum of the [CII] $158$~$\mu$m emission line during the Epoch of Reionization. TIME completed a commissioning run in 2022 at the Arizona Radio Observatory onboard the 12-M Radio Telescope at Kitt Peak, where it observed galactic sources for the first time. In this paper we report on an analysis of observations of the Orion Molecular Cloud (OMC) and G49.5 (a local HII region). The OMC observations were taken at least once a day to assess the stability of the instrument and demonstrate its on-sky performance. We describe a spectral image processing pipeline to make calibrated maps of raster scans of these sources, incorporating planet observations for gain calibration. We show with G49.5 that, when compared to the Bolocam Galactic Plane Survey, we are able to achieve a $< 3\%$ calibration difference. Based on the outcomes from this commissioning phase of TIME, we have demonstrated preliminary performance, and identified sources of improvement necessary for pursuing a LIM measurement.

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arXiv2025

TIME Commissioning Observations: I. Mapping Dust and Molecular Gas in the Sgr A Molecular Cloud Complex at the Galactic Center

We present the processing of an observation of Sagittarius A (Sgr A) with the Tomographic Ionized-carbon Mapping Experiment (TIME), part of the 2021-2022 commissioning run to verify TIME's hyperspectral imaging capabilities for future line-intensity mapping. Using an observation of Jupiter to calibrate detector gains and pointing offsets, we process the Sgr A observation in a purpose-built pipeline that removes correlated noise through common-mode subtraction with correlation-weighted scaling, and uses map-domain principal component analysis to identify further systematic errors. The resulting frequency-resolved maps recover strong 12CO(2-1) and 13CO(2-1) emission, and a continuum component whose spectral index discriminates free-free emission in the circumnuclear disk (CND) versus thermal dust emission in the 20 km s$^{-1}$ and 50 km s$^{-1}$ molecular clouds. Broadband continuum flux comparisons with the Bolocam Galactic Plane Survey (BGPS) show agreement to within $\sim$5% in high-SNR molecular clouds in the Sgr A region. From the CO line detections, we estimate a molecular hydrogen mass of between $5.4 \times 10^5 M_\odot$ and $5.7 \times 10^5 M_\odot$, consistent with prior studies. These results demonstrate TIME's ability to recover both continuum and spectral-line signals in complex Galactic fields, validating its readiness for upcoming extragalactic CO and [C II] surveys.

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arXiv2025

Development of a planar cable-driven parallel robot for submillimeter and terahertz beam mapping measurements

The spatial sensitivity pattern of millimeter-wavelength receivers is an important diagnostic of performance and is affected by the alignment of coupling optics. Characterization can be challenging in the field, particularly in the decentered and tightly packed optical configurations that are employed for many astronomical millimeter-wave cameras. In this paper, we present the design and performance of a lightweight and reconfigurable beam mapper, consisting of a bank of thermal sources positioned by a planar cable-driven robot. We describe how the measurement requirements and mechanical constraints of the Tomographic Ionized-carbon Mapping Experiment (TIME) optical relay drive the design of the mapper. To quantify the positioning performance, we predict the beam patterns at each surface to derive requirements and use a non-contact computer-vision based method built on OpenCV to track the payload position with an accuracy better than 1.0 mm. We achieve an in-plane absolute payload position error of 2.7 mm (RMSE) over a $\sim$400 mm $\times$ 400 mm workspace and an in-plane repeatability of 0.81 mm, offering substantial improvements in accuracy and speed over traditional handheld techniques.

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arXiv2024

Cosmic ray susceptibility of the Terahertz Intensity Mapper detector arrays

We report on the effects of cosmic ray interactions with the Kinetic Inductance Detector (KID) based focal plane array for the Terahertz Intensity Mapper (TIM). TIM is a NASA-funded balloon-borne experiment designed to probe the peak of the star formation in the Universe. It employs two spectroscopic bands, each equipped with a focal plane of four $\sim\,$900-pixel, KID-based array chips. Measurements of an 864-pixel TIM array shows 791 resonators in a 0.5$\,$GHz bandwidth. We discuss challenges with resonator calibration caused by this high multiplexing density. We robustly identify the physical positions of 788 (99.6$\,$%) detectors using a custom LED-based identification scheme. Using this information we show that cosmic ray events occur at a rate of 2.1$\,\mathrm{events/min/cm^2}$ in our array. 66$\,$% of the events affect a single pixel, and another 33$\,$% affect $<\,$5 KIDs per event spread over a 0.66$\,\mathrm{cm^2}$ region (2 pixel pitches in radius). We observe a total cosmic ray dead fraction of 0.0011$\,$%, and predict that the maximum possible in-flight dead fraction is $\sim\,$0.165$\,$%, which demonstrates our design will be robust against these high-energy events.

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