The airborne lunar spectral irradiance mission (Air-LUSI) is a partnership between NASA and NIST to create SI-traceable measurements of lunar spectral irradiance in an effort to improve the measurements of Earth observing satellites. These satellites monitor the weather, vegetation, ocean currents, pollution, and more. Using the light reflected from the moon as a constant absolute reference point for satellite calibration will allow for improvements to these satellites and consistency between data from different satellite instruments. Satellites will be able to calibrate in-orbit and over-time as sensors degrade.
The custom telescope used to acquire the data is installed into the wing pod of an Earth Resources-2 aircraft, which is a direct descendant of the U-2 spy plane. The ER-2 flies to an altitude of 70,000 feet allowing the telescope to measure the light from the moon above 95% of the Earth’s atmosphere. Reducing the distortion effect of the atmosphere allows Air-LUSI to characterize the spectral irradiance of the moon more accurately than ground-based measurements, and in a similar environment to the Low-Earth Orbit satellites that will make use of the calibration point.

Ultra Motion’s Role
An autonomous robotic telescope mount instrument subsystem (ARTEMIS) was created by Dr. S. Andrew Gadsden and his team in the Intelligent Control and Estimation laboratory at the University of Guelph (Ontario, Canada) in order to accurately track the moon during the flight. Two Ultra Motion Servo Cylinders were successfully employed to control the telescope’s elevation and azimuth throughout the flights. The ARTEMIS system had to operate flawlessly at 70,000 feet and in ambient temperatures as low as -60°C. External heating elements were used to maintain the temperature of the actuators throughout the flight. Custom self-heating Servo Cylinder firmware can be installed to use the motor as a heat generating element for applications that cannot make use of external heaters.
Telemetry was gathered from the actuator’s integrated controller in order to monitor the performance and health of the Servo Cylinder throughout the experiment. This included absolute position from the Phase Index® contactless sensor, actuator temperature, bus voltage, and actuator phase current. Real-time data from the Servo Cylinders provide insight into the overall performance of the system and increases the confidence of the ARTEMIS for future test flights.

Results
A demonstration flight campaign over five separate flights showed that the ARTEMIS successfully tracked the moon with a root-mean-squared-error of 0.11° tracking accuracy! The Air-LUSI experiment will continue to be used over the coming years to gather lunar irradiance data for a range of lunar phases. As the data set grows, a higher fidelity lunar spectral irradiance model can be produced and allow for improvements to a significant amount of Earth-observing satellites.

Read more about this project.

A video overview of the Air-LUSI mission is shown below:
https://www.youtube.com/watch?v=4pT2_sO-of8&feature=emb_title

Photo Credit: Ken Ulrich, NASA

Photo Credit: Ken Ulrich, NASA

 

Photo Credit: Ken Ulrich, NASA

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Telemetry recorded via the Servo Cylinder’s serial communication interface. The above graphs represent the azimuth actuator’s temperature and the elevation actuator’s absolute position during the five separate flights.

The Servo Cylinder is a popular choice for high reliability UAV control surface and utility linear actuator applications. The A-Series Servo Cylinder uses a brushless DC motor and contactless absolute position feedback to reduce wear and provide superior performance when compared to potentiometers and brushed DC solutions. The built-in control electronics offer a variety of communication interfaces including RC PWM, 4-20 mA in/out, ±10 VDC, RS-232, RS-422, CAN, and CANopen.

Our AM Servo Cylinder is designed to excel in harsh shock/vibe environments with IP65 dynamic and IP67 static ingress protection ratings. The D38999 receptacles provide military standard connections, and the on-board temperature, current, voltage, and humidity sensors allow for constant health monitoring of the servo actuator. Custom heater firmware is available that maintains a configurable controller temperature even in ambient environments < -40°C. The Servo Cylinder has an 8 to 36 VDC operating bus voltage, which is compliant with the majority of UAV power busses and will survive at >51 VDC.

The Servo Cylinder offers forces up to 530 lbf, strokes up to 7.75 inches, and speeds up to 14 in/s, allowing for high bandwidth control >15 Hz at small position amplitudes.

Conversions of control surfaces from rotary actuators to linear actuators can lead to increased performance and decreased cost/mass. Contact Ultra Motion Engineering to discuss your unmanned vehicle actuator requirements in detail. View Servo Cylinder performance and dimensions by using our online configurator here.