Project Scientist Role
SMAP was, in many ways, the project I had been working toward for most of my career. By the time I was appointed Project Scientist, I had spent decades studying how microwave signals interact with soil and vegetation — trying to understand what a satellite passing overhead could actually tell us about the moisture in the soil just beneath the surface. SMAP was the chance to put all of that to work at a scale that mattered.
As Project Scientist, my job was to be the scientific conscience of the mission — making sure that every engineering decision, every trade-off, every data product stayed true to what we were actually trying to measure. Naturally this led to many potential conflicts amongst science team members and between the science team and other elements of the project. Prior to approval as a funded mission I led the Science Definition Team and worked closely with the instrument engineers and algorithm developers at JPL and Goddard Space Flight Center. It was demanding, collaborative work, and required determination, persistence, and extensive diplomatic skills. I found it deeply satisfying, though towards the end of my service I began to weary of the role, especially as launch approached and the public relations machinery began to ramp up into full swing.
Mission Overview
SMAP launched on January 31, 2015, from Vandenberg Air Force Base — a moment I had been anticipating for the better part of a decade. The satellite was developed at JPL and Goddard Space Flight Center and is managed by JPL for NASA's Science Mission Directorate.
The mission was designed to do something fundamentally simple: measure how much water is held in the top 5 centimeters of soil across the entire globe, and tell us whether the ground is frozen or thawed. Those measurements turn out to be surprisingly important — they feed into weather forecasts, flood warnings, drought assessments, and climate models that affect people's lives in very direct ways.
- Launch Date
- January 31, 2015
- Launch Vehicle
- United Launch Alliance Delta II
- Orbit
- Near-polar, sun-synchronous, 685 km altitude
- Revisit Time
- 2–3 days globally
- Primary Instruments
- L-band radiometer (1.41 GHz) and L-band radar (1.26 GHz)
- Antenna
- 6-meter deployable mesh reflector
Science Objectives
Global Soil Moisture Mapping
Produce high-accuracy global maps of soil moisture in the top 5 cm of the land surface at 9 km resolution, updated on a 3-day cycle — a level of coverage and consistency that had never before been achieved from space.
Freeze/Thaw State Detection
Detect whether the land surface is frozen or thawed, which determines when ecosystems in high latitudes begin and end their growing seasons — and how much carbon they absorb or release in the process.
Water Cycle Understanding
Build a consistent, long-term record that illuminates the connections between Earth's water, energy, and carbon cycles — connections that are fundamental to understanding how the planet works and how it is changing.
Weather and Climate Applications
Put the data to practical use: improving numerical weather forecasts, flood and drought early warning systems, and agricultural monitoring — applications that translate directly into better decisions for communities around the world.
Key Outcomes and Legacy
SMAP has been operating continuously since April 2015, and the data record it has built is something something genuinely to be proud of. The L-band radiometer has performed well throughout, and the soil moisture products are assimilated into operational weather and climate models at forecasting centers around the world.
The mission has supported hundreds of peer-reviewed studies across hydrology, ecology, agriculture, and climate science. It demonstrated, in a way that no airborne campaign or theoretical paper could fully do, the value of sustained L-band observations from space — and it set a standard that future missions will build on.
When I look at the SMAP soil moisture products, I can trace a direct personal line back to the theoretical work I was doing in the mid- to late-1970s — the radiative transfer models, the retrieval algorithms, the early satellite experiments. It is a rare thing in science to be able to participate in that arc of completion. I feel fortunate to have been part of it.