nominal position are corrected at the beginning of the observational run. After a good match is obtained between the model and the observations, we propose to use a Zemax model to improve the wavelength calibration solution. We could match the observations and model within $\pm$ 1 pixels accuracy after the model parameters were perturbed in a real-time setup of the spectrograph. In this paper, we present the estimation of the perturbations of optical components and the effect on the RV obtained.'
author:
- Sireesha Chamarthi
- Ravinder K Banyal
- 'S. Sriram'
bibliography:
- 'report.bib'
title: 'Estimation and correction of the instrumental perturbations of VBT Echelle spectrograph using a model-based approach'
---

[**\***Sireesha Chamarthi, ]{}

[2]{}

Introduction {#sect:intro}
============

To utilize a high-resolution spectrograph for precision Doppler spectroscopy, a robust instrument design is essential for the desired performance. A dedicated RV spectrograph has several unique features such as fixed optomechanical components, optics fabricated with low expansion material. Along with this a vibration-free vacuum enclosure is essential to enforce a tight control of environmental conditions (temperature and pressure, etc) [@HARPS; @AFOE; @spectrographs]. Furthermore, the star-light from the telescope is fed through optical fibers for image scrambling and illumination stabilization. Along with 