Systematic Error Analysis of DORIS Range-Rate Residuals for Precise Orbit Determination of Radar Altimeter Satellites

Sushant Shekhar (National Centre for Geodesy, India)

Somalin Nath (NCG, IIT Kanpur, India); Rohit Singh Rana (NCG, IIT Kanpur, India); Onkar Dikshit (NCG, IIT K, India)

Event: 2026 IDS Workshop

Session: Advances in Satellite Dynamics and Orbit Determination

Presentation type: Poster

DOI: 10.24400/312072/i03-2026.4533

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Abstract

Several Earth observation missions equipped with radar altimeters rely on the Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) system for precise orbit determination (POD), which is essential for generating accurate geophysical products such as sea level variability and ice sheet elevation. The accuracy of these products is highly sensitive to orbit errors, as systematic biases can propagate into long-term climate datasets. Although DORIS provides stable and globally distributed observations, range-rate residuals—commonly used as a diagnostic measure of POD performance—often exhibit structured, non-random patterns, indicating the presence of unmodeled or mismodeled error sources within the observation and dynamic models.
In this study, long-term time series of DORIS range-rate residuals are analyzed across multiple satellite missions (HY-2A, Jason-3, Sentinel-6A, Sentinel-6B, and SARAL) and ground stations (DJIBOUTI, MALE, CIBINONG, and KITAB) to investigate systematic errors. The results reveal consistent elevation-dependent discrepancies, with larger residuals at low elevation angles, suggesting limitations in atmospheric modeling, antenna phase center corrections, and multipath effects. A detailed analysis of Sentinel-6A observations at the MAMC station (L2 GHz) on Day 64 shows pronounced systematic variations, with residuals reaching up to ~40 mm/s. Statistical evaluation of the MALE station dataset indicates a residual mean of 13.8 mm/s and a standard deviation of 8.39 mm/s, which reduce to 1.1 mm/s and 0.13 mm/s, respectively, after applying receiver clock synchronization corrections. These findings highlight the significant impact of clock-related errors and confirm the presence of common modeling deficiencies, emphasizing the need for improved correction strategies to enhance orbit determination accuracy and the reliability of derived geophysical products.

Contribution: IDS26_s3_Kumar_RangeRateAnalysis(poster).pdf (pdf, 559 ko)

Corresponding author:

Sushant Shekhar

National Centre for Geodesy

India

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