Fifteen years of the Advanced CCD Imaging Spectrometer

TL;DR

This paper reviews fifteen years of operation of the ACIS instrument on Chandra, highlighting its performance, calibration, and ongoing scientific contributions despite aging and radiation effects.

Contribution

It provides a comprehensive overview of ACIS's operational history, calibration methods, and future outlook based on monitoring data and performance analysis.

Findings

ACIS has maintained good performance over 15 years.

Calibration sources have been effective despite decay.

No significant limitations on ACIS lifetime are observed.

Abstract

As the Advanced CCD Imaging Spectrometer (ACIS) on the Chandra X-ray Observatory enters its fifteenth year of operation on orbit, it continues to perform well and produce spectacular scientific results. The response of ACIS has evolved over the lifetime of the observatory due to radiation damage, molecular contamination and aging of the spacecraft in general. Here we present highlights from the instrument team's monitoring program and our expectations for the future of ACIS. The ACIS calibration source produces multiple line energies and fully illuminates the entire focal plane which has greatly facilitated the measurement of charge transfer inefficiency and absorption from contamination. While the radioactive decay of the source has decreased its utility, it continues to provide valuable data on the health of the instrument. Performance changes on ACIS continue to be manageable, and do not indicate any limitations on ACIS lifetime.