The ASCENDS CarbonHawk Experiment Simulator

Type: Poster presentation

Venue: AGU Fall Meeting 2012


Michael D. Obland; Narasimha S. Prasad; Fenton W. Harrison; Edward V. Browell; Syed Ismail; Jeremy T. Dobler; Berrien Moore; T Scott Zaccheo; Joel Campbell; Songsheng Chen; Craig S. Cleckner; Mary DiJoseph; Alan Little; Anthony Notari; Tamer F. Refaat; David Rosenbaum; Michael D. Vanek; Joe Bender; Michael Braun; Arturo Chavez-Pirson; Mark Neal; Peter J. Rayner; Alex Rosiewicz; Mark Shure; Wayne Welch (2012) ACES: The ASCENDS CarbonHawk Experiment Simulator. AGU Fall Meeting 2012, San Francisco, CA.

The ASCENDS CarbonHawk Experiment Simulator (ACES) is a NASA Langley Research Center project funded by NASA’s Earth Science Technology Office (ESTO) Instrument Incubator Program (IIP) that seeks to advance technologies critical to measuring atmospheric column carbon dioxide (CO2) mixing ratios in support of the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission. The technologies being advanced are: (1) a high bandwidth detector, (2) a multi-aperture telescope assembly, (3) advanced algorithms for cloud and aerosol discrimination, and (4) high-efficiency, multiple-amplifier CO2 and O2 laser transmitters. The instrument architecture will be developed to operate on a high-altitude aircraft and will be directly scalable to meet the ASCENDS mission requirements. These technologies are viewed as critical towards developing an airborne simulator and eventual spaceborne instrument with lower size, mass, and power consumption, and improved performance.

The detector effort will improve the existing detector subsystem by increasing its bandwidth to a goal of 5 MHz, reducing its overall mass from 18 lbs to <10 lbs, and stretching the duration of autonomous, service-free operation periods from 4 hrs to >24 hrs. The development goals are to permit higher laser modulation rates, which provides greater flexibility for implementing thin-cloud discrimination algorithms as well as improving range resolution and error reduction, and to enable long flights on a high-altitude unmanned aerial vehicle (UAV).

The telescope development consists of a three-telescope design built for the constraints of the Global Hawk aircraft. This task addresses the ability of multiple smaller telescopes to provide equal or greater collection efficiency compared with a single larger telescope with a reduced impact on launch mass and cost. The telescope assembly also integrates fiber-coupled transmit collimators for all of the laser transmitters and fiber-coupled optical signal output to the aft optics and detector package.

The cloud/aerosol discrimination work features development by Langley and Exelis of new algorithms for the avoidance of bias errors in the return signal induced by the presence of thin clouds. Coupled with the advanced detector performance, this effort seeks to significantly mitigate thin cloud effects on the retrieval.

The laser transmitter development includes fabrication of high-efficiency fiber seed lasers, modulators, and amplifiers for sensing of both CO2 and O2. The 1.26 micron Master Oscillator Power Amplifier (MOPA) is meant to resonantly probe O2 using an Integrated-Path Differential Absorption Lidar (IPDA) approach similar to that of the CO2 transmitter. Wavelengths near 1.26 microns are not readily available from commercial off-the-shelf (COTS) lasers, and thus laser technology is being advanced in this area to demonstrate the performance necessary for a space payload.

ACES leverages the Exelis Multi-function Fiber Laser Lidar instrument, which has previously flown on numerous test flights, to demonstrate the ACES technologies.