Antonios Seas

Space laser transmitter development for ICESat-2 mission

The first NASA Ice, Cloud and land Elevation Satellite (ICESat) was launched in January 2003 and placed into a nearpolar orbit whose primary mission was the global monitoring of the Earths ice sheet mass balance. ICESat has accumulated over 1.8 B shots in space and provided a valuable dataset in the study of ice sheet dynamics over the past few years. NASA is planning a follow-on mission ICESat-2 to be launched tentatively in 2015. In this paper we will discuss the development effort of the laser transmitters for the ICESat-2 mission.

The Slope Imaging Multi-polarization Photon-counting Lidar: Development and performance results

The Slope Imaging Multi-polarization Photon-counting Lidar is an airborne instrument developed to demonstrate laser altimetry measurement methods that will enable more efficient observations of topography and surface properties from space. The instrument was developed through the NASA Earth Science Technology Office Instrument Incubator Program with a focus on cryosphere remote sensing. The SIMPL transmitter is an 11 KHz, 1064 nm, plane-polarized micropulse laser transmitter that is frequency doubled to 532 nm and split into four push-broom beams. The receiver employs single-photon, polarimetric ranging at 532 and 1064 nm using Single Photon Counting Modules in order to achieve simultaneous sampling of surface elevation, slope, roughness and depolarizing scattering properties, the latter used to differentiate surface types. Data acquired over ice-covered Lake Erie in February, 2009 are documenting SIMPLs measurement performance and capabilities, demonstrating differentiation of open water and several ice cover types. ICESat-2 will employ several of the technologies advanced by SIMPL, including micropulse, single photon ranging in a multi-beam, push-broom configuration operating at 532 nm.

Results of the MIT Space Communication and Navigation architecture study

NASA is currently conducting an architecture study for the next-generation Space Communication and Navigation system. This is an extremely complex problem with a variety of options in terms of band selection (RF, from S-band to Ka-band and beyond, or optical), network type (bent-pipe, circuit-switched, or packet-switched), fractionation strategies (monolithic, mother-daughters, homogeneous fractionation), orbit and constellation design (GEO/MEO/LEO, number of planes, number of satellites per plane), and so forth. When all the combinations are considered, the size of the tradespace grows to several millions of architectures. The ability of these architectures to meet the requirements from different user communities and other stakeholders (e.g., regulators, international partners) needs to be assessed. In this context, a computational tool was developed to enable the exploration of such large space of architectures in terms of both performance and cost. A preliminary version of this tool was presented in a paper last year. This paper describes an updated version of the tool featuring a higher-fidelity, rule-based scheduling algorithm, as well as several modifications in the architecture enumeration and cost models. It also discusses the validation results for the tool using real TDRSS data, as well as the results and sensitivity analyses for several forward-looking scenarios. Particular emphasis is put on families of architectures that are of interest to NASA, namely TDRSS-like architectures, architectures based on hosted payloads, and highly distributed architectures.

Exploring the architectural trade space of NASAs Space Communication and Navigation Program

NASAs Space Communication and Navigation (SCaN) Program is responsible for providing communication and navigation services to space missions and other users in and beyond low Earth orbit. The current SCaN architecture consists of three independent networks: the Space Network (SN), which contains the TDRS relay satellites in GEO; the Near Earth Network (NEN), which consists of several NASA owned and commercially operated ground stations; and the Deep Space Network (DSN), with three ground stations in Goldstone, Madrid, and Canberra. The first task of this study is the stakeholder analysis. The goal of the stakeholder analysis is to identify the main stakeholders of the SCaN system and their needs. Twenty-one main groups of stakeholders have been identified and put on a stakeholder map. Their needs are currently being elicited by means of interviews and an extensive literature review. The data will then be analyzed by applying Cameron and Crawleys stakeholder analysis theory, with a view to highlighting dominant needs and conflicting needs. The second task of this study is the architectural tradespace exploration of the next generation TDRSS. The space of possible architectures for SCaN is represented by a set of architectural decisions, each of which has a discrete set of options. A computational tool is used to automatically synthesize a very large number of possible architectures by enumerating different combinations of decisions and options. The same tool contains models to evaluate the architectures in terms of performance and cost. The performance model uses the stakeholder needs and requirements identified in the previous steps as inputs, and it is based in the VASSAR methodology presented in a companion paper. This paper summarizes the current status of the MIT SCaN architecture study. It starts by motivating the need to perform tradespace exploration studies in the context of relay data systems through a description of the history NASAs space communication networks. It then presents the generalities of possible architectures for future space communication and navigation networks. Finally, it describes the tools and methods being developed, clearly indicating the architectural decisions that have been taken into account as well as the systematic approach followed to model them. The purpose of this study is to explore the SCaN architectural tradespace by means of a computational tool. This paper describes the tool, while the tradespace exploration is underway.

Overview of space qualified solid state lasers development at NASA Goddard Space Flight Center

NASA Goddard Space Flight Center (GSFC) has been engaging in Earth and planetary science instruments development for many years. With stunning topographic details of the Mars surface to Earths surface maps and ice sheets dynamics of recent years, NASA GSFC has provided vast amount of scientific data products that gave detailed insights into Earths and planetary sciences. In this paper we will review the past and present of space-qualified laser programs at GSFC and offer insights into future laser based science instrumentations.

Seeded nanosecond optical parametric generator for trace gas measurements

We report on the development effort of a nanosecond-pulsed seeded optical parametric generator (OPG) for remote trace gas measurements. The seeded OPG output light is single frequency with high spectral purity and is widely tunable both at 1600nm and 3300nm with an optical-optical conversion efficiency of ~40%. We demonstrated simultaneous tuning over the methane (CH4) absorption line at idler wavelength, 3270.4nm, and carbon dioxide (CO2) absorption line at signal wavelength, 1578.2nm. In this paper, we will also discuss open-path atmospheric measurements with this newly developed laser source.

Quasi-CW laser diode arrays for space applications

NASAs space-borne laser missions have been dominated by low repetition rate (<100Hz) Q-switched laser systems, which use Nd:YAG laser crystals, and are pumped by quasi-continuous wave (QCW) 808 nm laser diode arrays (LDAs). The diode group at NASA Goddard Space Flight Center (GSFC) has been responsible for the screening and qualification of LDAs for several missions. The main goal has been to identify LDAs that can withstand the harsh space environment, and minimize risks associated with LDA degradation or failure. This paper presents a summary of recent research activities, and describes the results from extended testing of multiple LDAs in air and vacuum environments.

Qualification of laser diode arrays for space applications

In the recent past, NASAs space-borne laser missions have been dominated by low repetition rate (<100Hz), Q-switched Nd:YAG lasers pumped by quasi-continuous wave (QCW) 808 nm laser diode arrays (LDA). QCW LDA reliability data is limited and their mechanisms of failure is poorly understood. Our group has been working in gathering statistically significant data on these devices and have developed testing strategies to achieve mission success in a cost-effective manner. In this paper, we present our approach for qualifying the LDAs for the Lunar Orbiter Laser Altimeter (LOLA) instrument scheduled to launch aboard the Lunar Reconnaissance Orbiter (LRO) mission. We describe our strategy to mitigate risk due to LDA failure given cost and schedule constraints. The results from extended testing of multiple LDAs in air and in vacuum are also presented.

Development and Vacuum Life Test of a Diode-Pumped Cr:Nd:YAG Laser (Heritage Laser) for Space Applications

The development and vacuum life-testing of a diode pumped Cr:Nd:YAG laser for space applications is presented. Furthermore results from long life-testing of 808-nm laser diode arrays in air and vacuum are discussed.

885-nm laser diode array pumped ceramic Nd:YAG master oscillator power amplifier system

The objective of this effort is to develop more reliable, higher efficiency diode pumped Nd:YAG laser systems for space applications by leveraging technology investments from the DoD and other commercial industries. Our goal is to design, build, test and demonstrate the effectiveness of combining 885 nm laser pump diodes and the use of ceramic Nd:YAG for future flight missions. The significant reduction in thermal loading on the gain medium by the use of 885 nm pump lasers will improve system efficiency.