Introduction

Earth Observation Quality Control (EOQC) is in charge of routinely monitoring the quality of European Landsat products since the beginning of EOQC activities in 2001. This document gathers together principal investigations on anomalies that occasionally occur in Landsat products. This document has been designed as support for the Landsat product rejection flow and is now available to users. It should be considered as a basis for communication between ESA User Services and Landsat product users and experts.

This anomaly inventory is not exhaustive and additional in-depth investigations are reported as well, thanks to USGS Landsat team experts. Detailed explanations can be viewed on the USGS website, http://landsat.usgs.gov/investigations.html.

The Landsat anomaly inventory contains the following anomaly reports, one sub-section per anomaly. Each report presents a description of the problem, its causes, its consequences, different workarounds and measures to prevent it and correct it. It proposes as well indications (references, URLs) on how to go further.

Contents

Ephemeris and attitude

Product geometric accuracy is in part strongly dependent on ephemeris and attitude metadata reliability. This report deals with anomalies due to inconsistent and shifted ephemeris and attitude records and their consequences on product location accuracy.

Swath and line misalignment

The present report is dedicated to anomalies such as large or small swath shift and line or detector displacement anomalies. Anomaly causes and consequences on product quality are explained. Some explanations are given to discern real swath displacements from "natural offset" due to inclination of sub-horizontal structures (streets, field boundaries, beach...) and due to image geometric corrections.

Missing image data

This part addresses anomalies due to missing image data such as missing pixels, missing swath - speckle ... Root causes differ strongly from one anomaly to the other one. In some cases real pixel values can be recovered. This document provides the user with basic steps for implementing a repair process.

Gain change

Gain change only occurs on the ETM+ instrument on board Landsat 7. Gain change cannot be considered as an anomaly but remains a user rejection cause. This report aims at explaining gain change phenomena and proposes to the user basic elements for detecting himself if the scene to be ordered is or will be contaminated by a gain change.

Striping

Striping anomalies occur at scene "line" level and are due to detector-to-detector mis-calibration. This reports clarifies the main causes of this anomaly and assess its consequences on radiometric product quality.

Banding

This report addresses common radiometric artifacts mainly occurring at scene swath level on Landsat 4 and Landsat 5 TMs and classified as memory effect, scan line correlated shift and coherent noise.

Detector oversaturation

This anomaly, commonly known as the "comet-like" artifact, is caused by a very bright object on the ground that exceeds the dynamic range of the instrument. This report proposes precise investigation for better understanding the phenomenon.

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry