C-20A

Airborne Science Research Aircraft

NASA's Armstrong Flight Research Center 

operates a C-20A, a military version of the 

Gulfstream III business jet, as an airborne 

science research aircraft for a variety of geophysical research missions. The aircraft was 

extensively modified and instrumented for the 

role, including installation of a sophisticated 

synthetic aperture radar in an underbelly pod, 

a self-contained on-board Data Collection and 

Processing System (DCAPS), and the Platform 

Precision Autopilot (PPA) system that enables 

the aircraft to fly repeat passes over a target 

within a 15 foot diameter “tube” of the original 

flight path.

The twin-turbofan aircraft provides long-term 

capability for efficiently conducting airborne 

environmental science missions for NASA, 

other government agencies, academia, and 

private industry.

Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) 

The UAVSAR is a sophisticated system developed by NASA's Jet Propulsion Laboratory 

(JPL) in Pasadena, California. Built initially 

for carriage by remotely piloted aircraft, the 

UAVSAR is mounted on the C-20A in a specially designed pod that will be interoperable 

with uncrewed aircraft in the future.

The UAVSAR uses a technique called interferometry to detect and measure very subtle 

deformations in Earth's surface. The sensor is 

designed to gather data for geological studies 

on earthquakes and volcanoes, ice and glacier 

movement supporting climate change studies, 

biological studies supporting ecology and carbon cycle science, and oceanography research.

Since the UAVSAR was installed in 2007, the 

aircraft has flown more than 4,500 flight hours 

for data collection.

To support installation of the UAVSAR pod, 

the C-20A airframe was structurally modified 

to incorporate a MAU-12 ejector rack on the 

bottom of the fuselage. This unique modification will remain available for use by future 

NASA’s Armstrong Flight Research Center in Edwards, California, flew the C-20A aircraft in support of the 

Advanced Synthetic Aperture Radar (ASAR) campaign. (NASA)
FS-2022-11-089 AFRC

National Aeronautics and Space Administration

Armstrong Flight Research Center

P.O. Box 273

Edwards, California 93523

NASA Facts

projects. The modified rack, with power and data connectivity to equipment in the aircraft cabin, can accommodate 

various external pods to carry specialized science instruments.

Data Collection and Processing System (DCAPS)

NASA Armstrong's C-20A airborne science research 

aircraft is equipped with a self-contained on-board instrumentation system that allows for automated configuration setups to reduce required engineering support 

for each mission. Primary and backup systems assure 

mission reliability, with the backup system available 

for use concurrently as a parallel system when needed. 

The DCAPS is designed to allow easy upgrades, addition of add-on systems for expansion, and can operate 

in autonomous and manual modes.

The custom DCAPS installed on the C-20A was developed to enable processing, distributing, displaying, and 

archiving aircraft flight data and customers’ experimental data in real time.

Precision Platform Autopilot (PPA)

The aircraft features a high-precision autopilot designed 

and developed by engineers at NASA Armstrong. The 

PPA guides the aircraft using a kinematic differential 

Global Positioning System developed by JPL and the aircraft's inertial navigation system to enable it to fly repeat 

paths to an accuracy of 15 feet or less. With the precision 

autopilot engaged, the synthetic aperture radar can acquire 

repeat-pass data that can measure land-surface changes 

within millimeters. 

Other Modifications

In addition, the aircraft features a video collection and 

distribution system and several satellite communications 

systems, including airborne internet connectivity, satellite 

phones/texting hotspots, and an upgraded 115VAC, 60HZ 

electrical power system.

Aircraft Description

NASA Armstrong's C-20A was obtained from the U.S. 

Air Force in September 2002. It bears tail number (TN) 

802 and is based at Armstrong’s Building 703 in Palmdale, California.

The Gulfstream III/C-20A aircraft were built by Gulfstream Aerospace Corp. In the aircraft’s commercial 

version, the G-III’s basic role is as an executive business 

aircraft that can carry up to 12 passengers. The C-20B version, flown by the Air Force, serves in a similar capacity 

for high-level government and military officials.

The C-20A's maximum takeoff weight with full fuel and 

passengers or cargo is 69,700 pounds. The unmodified 

airplane weighs about 38,000 pounds empty. The aircraft 

has a wingspan of approximately 7 feet, is 83 feet long, 

and 24 feet tall. Normal cruise for the aircraft is 527 mph 

(459 knots) and its top speed is 576 mph (501 knots; 

Mach 0.85). The C-20A's maximum operating altitude 

is 45,000 feet and it has a range with a full load of passengers or equipment of about 3,400 nautical miles (4,000 

statute miles).

Two Rolls-Royce Spey Mark 511-8 turbofan engines, 

each producing 11,400 pounds (5,170 kilograms) of 

thrust, power the aircraft.

A forest of tufts are mounted on the underbelly and pylon 

of NASA's Gulfstream-III research aircraft to help engineers 

determine airflow around the UAVSAR pod. (NASA)