Airborne Lunar Spectral Irradiance

Status

Status
Operational
Operated By
PI

Air-LUSI makes highly-accurate, SI-traceable measurements of lunar spectral irradiance.  These measurements can be used to validate or adjust current models of lunar spectral irradiance used for calibration Earth observing satellites.  Air-LUSI is initially being used to address the current 5-10% uncertainty in knowledge of exo-atmospheric spectral lunar irradiance. Improved lunar spectral irradiance model accuracy will help satellite instruments to use the Moon as an absolute calibration reference, greatly improving the versitility and speed of on-orbit satellite calibration.  Air-LUSI has two main subsystems:

  • IRIS - IRradiance Instrument Subsystem is a non-imaging telescope with an integrating sphere feeding light via fiber optics to a spectrometer.
  • ARTEMIS - Autonomous, Robotic TElescope Mount Instrument Subsystem keeps telescope fixed on the Moon to within less than 0.1°.  This system uses a tracking camera on the telescope and control computer.

We are targeting lunar phases withing 5° to 90° of the Full Moon.  Air-LUSI measurements lunar spectral irradiance with spectral resolution of 3.7 nm with 0.8 nm sampling from 300 nm to 1100 nm, with accuracy target of better than 1% (k=1).  Future system performance will include measurements out to 2500 nm with ≤ 10 nm resolution.  Demonstration flights with the Air-LUSI provided an unprecedented sub-percent level of accuracy <0.8% (k=1) relative uncertainty from 400 nm to 950 nm.  Future measurement accuracy is expected to be <0.5% (k=1).

Instrument Type
Aircraft
Recent Missions
(ER-2 - AFRC)
;
(ER-2 - AFRC)
;
(ER-2 - AFRC)
;
(ER-2 - AFRC)
Point(s) of Contact
(POC; PI)
Range of Measurement
Other
Instrument Pointing
Upwards pointing but not directly upwards
Pointing Angles
265° - 275° from heading
Measurement Wavelengths
Has Pressurized Canisters? Yes
Location
The Air-LUSI system is installed in the ER-2 superpod (either port or starboard of the #809 or #806). The frequency converter and robotic control assemble is situated in the rack in the front of the mid-body, the instrument enclosure is placed in the middle bay of the mid-body and the telescope and its robotic mount is in the aft-body portion of the superpod. Cable harnesses run through the bulkhead between the mid-body and aft-body, carrying electronic and fiber optic cables.
Notes
Air-LUSI requires pre and post campaign calibration, on-site and at NIST before and after deployment. Additional calibration checks are performed between flights.
Air-LUSI flies at night to observe the Moon. Typical campaign is done out of AFRC, with a generally east-west to northeast-southwest flight path, oriented to keep the Moon about 90° to port. Robotic mount keeps the telescope tracking the Moon, compensating for aircraft motion.
TRL
8