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Measuring Precipitable Water Vapor through Dual-Band GPS at Rubin Observatory

  • Anja Weyant
  • W. M. Wood-Vasey
  • Elana K. Urbach
  • Sara Gelven
  • Marcos Tamargo-Arizmedi
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Abstract

Precipitable water vapor (PWV) in Earth's atmosphere is a known source of systematic error in ground-based astronomical measurements, particularly at wavelengths greater than 7,000 angstroms. PWV produces wavelength-dependent extinction in the spectral energy distributions of observed sources. For high-precision applications, such as supernova cosmology, the transmission function must be measured accurately and precisely for each observation. The Vera C. Rubin Observatory is located in the Chilean Andes, a region known for dry conditions. However, even at this location, time-variable absorption by water vapor is a factor. Signal delays from Global Navigation Satellite Systems (GNSS) offer a robust, easy, 24-hour monitoring of PWV. In this paper we present measurements from the first six months of GNSS-PWV at Rubin Observatory. We verified our analysis by replicating results from the International GNSS Service (IGS), demonstrating high consistency. We then installed and commissioned a Trimble Net R9 receiver at Allegheny Observatory for a commissioning run before it was relocated to Rubin Observatory. At Rubin Observatory we have been continuously measuring PWV since 2025 September 5. We find average PWV levels of 3.0 kg/m2 in Southern Hemisphere spring (September to November) and 5.4 kg/m2 in summer (December to February). The PWV at Rubin also has a clear daily variation with an amplitude of 1.2-3.8 kg/m2 that is highly correlated with the east-west wind strength. We conclude that the proposed GNSS-based processing method achieves an accuracy of 0.9 kg/m2 with 0.36 kg/m2 precision, confirming the capability for continuous, high-temporal-resolution PWV monitoring to support demanding LSST science cases.

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Cite

BibTeXRIS
BibTeX
@misc{weyant2026measuring,
  title = {{Measuring Precipitable Water Vapor through Dual-Band GPS at Rubin Observatory}},
  author = {Anja Weyant and W. M. Wood-Vasey and Elana K. Urbach and Sara Gelven and Marcos Tamargo-Arizmedi},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.40363},
  eprint = {2610.40363},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.40363},
}
RIS
TY  - UNPB
TI  - Measuring Precipitable Water Vapor through Dual-Band GPS at Rubin Observatory
AU  - Anja Weyant
AU  - W. M. Wood-Vasey
AU  - Elana K. Urbach
AU  - Sara Gelven
AU  - Marcos Tamargo-Arizmedi
PY  - 2026
DA  - 2026/10/29
PB  - arXiv
DO  - 10.48550/arxiv.2610.40363
UR  - https://arxiv.org/abs/2610.40363
AB  - Precipitable water vapor (PWV) in Earth's atmosphere is a known source of systematic error in ground-based astronomical measurements, particularly at wavelengths greater than 7,000 angstroms. PWV produces wavelength-dependent extinction in the spectral energy distributions of observed sources. For high-precision applications, such as supernova cosmology, the transmission function must be measured accurately and precisely for each observation. The Vera C. Rubin Observatory is located in the Chilean Andes, a region known for dry conditions. However, even at this location, time-variable absorption by water vapor is a factor. Signal delays from Global Navigation Satellite Systems (GNSS) offer a robust, easy, 24-hour monitoring of PWV. In this paper we present measurements from the first six months of GNSS-PWV at Rubin Observatory. We verified our analysis by replicating results from the International GNSS Service (IGS), demonstrating high consistency. We then installed and commissioned a Trimble Net R9 receiver at Allegheny Observatory for a commissioning run before it was relocated to Rubin Observatory. At Rubin Observatory we have been continuously measuring PWV since 2025 September 5. We find average PWV levels of 3.0 kg/m^2 in Southern Hemisphere spring (September to November) and 5.4 kg/m^2 in summer (December to February). The PWV at Rubin also has a clear daily variation with an amplitude of 1.2-3.8 kg/m^2 that is highly correlated with the east-west wind strength. We conclude that the proposed GNSS-based processing method achieves an accuracy of 0.9 kg/m^2 with 0.36 kg/m^2 precision, confirming the capability for continuous, high-temporal-resolution PWV monitoring to support demanding LSST science cases.
ER  -