# An Accurate Doppler Parameters Calculation Method of Geosynchronous SAR Considering Real-Time Zero-Doppler Centroid Control

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## Abstract

**:**

## 1. Introduction

## 2. Real-Time Zero-Doppler Centroid Control

#### 2.1. Accurate Attitude Steering Control

**Q**= $\mathit{R}$/R is the unit vector of the radar line of sight (RLS). Further derivation is carried out in the MCO CS, so vectors

**P**and

**Q**can be expressed as:

**Q**by matrix operators. In this paper, we only consider the pitch-yaw steering attitude control; the zero-Doppler centroid controlling equation can be expressed as:

#### 2.2. Attitude Steering Implement Method

## 3. Accurate Doppler Model

## 4. Simulations

## 5. Discussion

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 3.**Squint and look-down angles along the orbit. (

**a**) The eccentricity is 10

^{−8}; (

**b**) The eccentricity is 0.01.

**Figure 4.**Variations of the RLS during the synthetic aperture time. (

**a**) The eccentricity is 10

^{−8}; (

**b**) the eccentricity is 0.01.

**Figure 5.**Doppler centroid along the orbit at different eccentricities. (

**a**,

**c**,

**e**) consider the variation of the RLS, and the eccentricity is 10

^{−8}, 0.01, and 0.1, respectively. (

**b**,

**d**,

**f**) without considering the variation of the RLS compared to (

**a**,

**c**,

**e**).

**Figure 7.**Synthetic aperture time along the orbit. (

**a**) With the consideration of variations of the RLS; (

**b**) without the consideration of variations of the RLS.

**Figure 8.**Doppler bandwidth along the orbit. (

**a**) With the consideration of variations of the RLS; (

**b**) without the consideration of variations of the RLS.

**Figure 9.**Azimuth resolution along the orbit. (

**a**) With the consideration of variations of the RLS; (

**b**) without the consideration of variations of the RLS.

Parameter | Value | Parameter | Value |
---|---|---|---|

Semi-major axis | 42,164.17 km | Right ascension of ascending | 115° |

Eccentricity | 1 × 10^{−8} | Perigee | 270° |

Orbital inclination | 60° | Incident angle | 20° |

Carrier frequency | 1.25 GHz | Antenna size | 30 m × 30 m |

Pulse duration | 2.5 μs | Chirp bandwidth | 30 MHz |

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**MDPI and ACS Style**

Chang, F.; Yu, C.; Li, D.; Ji, Y.; Dong, Z.
An Accurate Doppler Parameters Calculation Method of Geosynchronous SAR Considering Real-Time Zero-Doppler Centroid Control. *Remote Sens.* **2021**, *13*, 4061.
https://doi.org/10.3390/rs13204061

**AMA Style**

Chang F, Yu C, Li D, Ji Y, Dong Z.
An Accurate Doppler Parameters Calculation Method of Geosynchronous SAR Considering Real-Time Zero-Doppler Centroid Control. *Remote Sensing*. 2021; 13(20):4061.
https://doi.org/10.3390/rs13204061

**Chicago/Turabian Style**

Chang, Faguang, Chunrui Yu, Dexin Li, Yifei Ji, and Zhen Dong.
2021. "An Accurate Doppler Parameters Calculation Method of Geosynchronous SAR Considering Real-Time Zero-Doppler Centroid Control" *Remote Sensing* 13, no. 20: 4061.
https://doi.org/10.3390/rs13204061