Digital Geography

Landsat-8: how not to plan a mission (Part 2: the sensors)

In my previous post I described the difficult process that led to the launch of Landsat-8. Here I will comment on the two sensors, the Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS), that comprise the sensor package on the Landsat-8 (L8) platform. This post will come across as highly critical, in some ways it is. I do want to point out though, at the start, that I appreciate the work of NASA and the USGS in securing the future of the Landsat programme: a program of global importance. In fact the programme has been so chaotic and ad…

Landsat-8: how not to plan a mission (Part 1: policy)

I was recently reading the 2012 article by James R. Irons and colleagues describing the Landsat-8 mission (or Landsat Data Continuity Mission, LDCM, as it was then called)¹. They do a very good job in describing the mission from planning to inception. I like to think of this paper as a guide to how not to plan an Earth Observation mission. Here’s my reasoning. Landsat-8’s difficult conception The logic behind Landsat-8 (L8) is impeccable. US agencies had realised that operational remote sensing, including at the Department of Agriculture and the United States Geological Survey (USGS), not to mention science, relied on…

What is the synthetic aperture in “Synthetic Aperture Radar” (SAR)?

Talking to a colleague recently about monitoring changes to the magrove forest of the Rufiji Delta in tanzania, he commented on the relative scarcity of satellite data over the region. It’s too cloudy. Some Landsat TM data exist: we found four images between 1989 and 2010 with less than 20% cloud over the northern delta. To observe the forest we will develop tools that use cloud penetrating synthetic aperture radar (SAR) data. SARs transmit microwaves at centimetre wavelengths (normally) that can penetrate cloud and can image the surface day or night. The intensity and polarisation of reflected or “backscattered” radar…