NASA Goddard Space Flight Center   Geodesy and Geophysics Laboratory  

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International Path Delay Service

Summary

The International Path Delay Service uses the output of numerical weather models and computes slant path and zenith path delays in the atmosphere at radio, infra-red or optic ranges, including dry and wet components. In addition, it computes atmospheric opacity and atmosphere brightness temperature in a range of 1 to 360 GHz. The service solves for logistic problems of downloading voluminous datasets, their preprocessing, performing CPU-intensive computations at a dedicated server, and presenting the results in a form that can be used for analysis of GNSS, SLR, DORIS, VLBI, radioastronomy, InSAR, air-born and space-born altimetry. The service provides access to data products that can either be used directly or via client software.

The goal of the Path Delay Service is to ingest outputs of numerical models, compute path delay through the neutral atmosphere, as well as related data products, and to disseminate the results for the entire scientific community on a regular basis, continuously, and with latencies 6—15 hours. The service is provided free of charge, and no registration is required.

Slant path delay through the neutral atmosphere in a form of 3D time series, as well as surface air pressure, surface partial pressure of water vapor, and air temperature is provided for 459 space geodesy and radioastronomy sites as a function of elevation, azimuth, and time.

Atmospheric opacity and atmosphere brightness temperature time series are provided for 314 space geodesy and radioastronomy sites as a function of elevation and frequency.

Download

In total, there are 355822 files to download from this site. To facilitate downloading files with slant path delay, opacthe list of URLs for downloading can be generating by filling a web form:
  1. Downloading pre-computed time series of slant path delay for 459 space geodesy and radioastronomy sites. This form will generate a list URLs of individual files or a control file for wget. The series are updated within 1 hour of availability of new output of numerical weather models.

  2. Downloading pre-computed time series of extended atmospheric propagation data products for 314 space geodesy and radioastronomy sites. This form will generate a list URLs of individual files or a control file for wget. The series are updated within 1 hour of availability of new output of numerical weather models.

Software

Software SPD for computing computing slanted path delay through the neutral atmosphere using the output of numerical weather models and for the end-user who needs only interpolation of slant path delay for data reduction can be found here.

Acknowledgment

This work was supported by NASA Earth Surface & Interior program, grant NNX12AQ29G.

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