NASA Goddard Space Flight Center is developing a master oscillator power amplifier (MOPA) laser transmitter for the ESA-led Laser Interferometer Space Antenna (LISA) mission. Taking advantage of our space laser experience and the emerging telecom laser technology, we are developing a full laser system for the LISA mission. Our research effort has included both master oscillator (MO) and power amplifier (PA) developments, and their environmental testing and reliability for space flight. Our current baseline for the MO is a low-mass, compact micro non-planar ring oscillator (m- NPRO) laser. The amplifier uses a robust mechanical design based on fiber components. We have performed laser system noise tests by amplitude- and frequency-stabilizing the PA output. We will describe our progress and plans to demonstrate a TRL 6 laser system, which is an essential step toward qualifying lasers for space applications, by 2021.
A highly stable and long-lifetime laser system is a key component of the space-based Laser Interferometer Space Antenna (LISA) mission, which is designed to detect gravitational waves from various astronomical sources. We are developing such laser system at the NASA Goddard Space Flight Center (GSFC). Our baseline architecture for the LISA laser consists of a low-power, low-noise small Nd:YAG non-planar ring oscillator (micro NPRO) followed by a diodepumped Yb-fiber amplifier with ~2 W output. In this paper, we will describe our progress to date and plans to demonstrate a technology readiness level (TRL) 6 LISA laser system.
ISS-TAO is a mission selected for a concept study by NASA, and proposed by GSFC for launch to the International Space Station (ISS) in order to observe transient high-energy astrophysical sources. It is composed of an X-ray Wide-Field Imager (WFI), and a multi-directional Gamma-ray Transient Monitor (GTM). WFI will be built by NASA/GSFC while the secondary GTM, described in this article is contributed by the Israel Space Agency (ISA) and developed at the Technion, Israel Institute of Technology, in collaboration with Israel space industries. ISS-TAO's main science goal is to detect electromagnetic (EM) counterparts to gravitational waves (GW) detected by GW observatories, such as the Laser Interferometer GW Observatory (LIGO). Observations of simultaneous GW and EM counterparts will address fundamental questions on the nature of coalescing neutron stars and black holes as astrophysical GW sources. An EM detection will also increase LIGO’s sensitivity to detecting these events above the GW background. Promising candidates for LIGO GW sources and EM counterparts are coalescing neutron star binaries, which are now known to also emit a short Gamma-Ray Burst (sGRB). The GTM will measure these GRBs and other transient gamma-ray events, and will trigger the WFI, with or without a GW trigger. The concept of the GTM detector consists of a compact configuration of 4 segments, which will allow a fair angular resolution of a few hundred square degrees, which will facilitate a prompt follow up. Each of the GTM segments consists of a crystal scintillator, a photo-multiplier tube (PMT), followed by analog and digital electronics designed to reconstruct the energy of each incoming photon, and to yield the light-curve and spectrum of any gamma-ray transient. A central CPU then calculates the ratio of the signal of each one of the segments, and deduced the transient position relative to the GTM.
A highly stable and robust laser system is a key component of the space-based Laser Interferometer Space Antenna (LISA) mission, which is designed to detect gravitational waves from various astronomical sources. The baseline architecture for the LISA laser consists of a low-power, low-noise Nd:YAG non-planar ring oscillator (NPRO) followed by a diode-pumped Yb-fiber amplifier with ∼2 W output. We are developing such laser system at the NASA Goddard Space Flight Center (GSFC), as well as investigating other laser options. In this paper, we will describe our progress to date and plans to demonstrate a technology readiness level (TRL) 6 LISA laser system.
ISS-Lobster is a wide-field X-ray transient detector proposed to be deployed on the International Space Station. Through its unique imaging X-ray optics that allow a 30 deg by 30 deg FoV, a 1 arc min position resolution and a 1.6x10<sup>-11 </sup>erg/(sec cm<sup>2</sup>) sensitivity in 2000 sec, ISS-Lobster will observe numerous events per year of X-ray transients related to compact objects, including: tidal disruptions of stars by supermassive black holes, supernova shock breakouts, neutron star bursts and superbursts, high redshift Gamma-Ray Bursts, and perhaps most exciting, X-ray counterparts of gravitational wave detections involving stellar mass and possibly supermassive black holes. The mission includes a 3-axis gimbal system that allows fast Target of Opportunity pointing, and a small gamma-ray burst monitor. In this article we focus on ISS-Lobster measurements of X-ray counterparts of detections by the world-wide ground-based gravitational wave network.
NASA is currently developing several Earth science laser missions that were recommended by the US National Research
Council (NRC) Earth Science Decadal Report. The Ice Cloud and Land Elevation Satellite-2 (ICESat-2) will carry the
Advanced Topographic Laser Altimeter System (ATLAS) is scheduled for launch in 2016. The Active Sensing of CO<sub>2</sub>
Emissions over Nights, Days, and Seasons (ASCENDS) mission and will measure column atmospheric CO<sub>2</sub>
concentrations from space globally. The Gravity Recovery And Climate Experiment (GRACE) Follow-On (GRACEFO)
and GRACE-2 missions measure the spatially resolved seasonal variability in the Earth's gravitational field. The
objective of the Lidar Surface Topography (LIST) mission is to globally map the topography of the Earth's solid surface
with 5 m spatial resolution and 10 cm vertical precision, as well as the height of overlying covers of vegetation, water,
snow, and ice. This paper gives an overview of the laser transmitter and receiver approaches and technologies for
several future missions that are being investigated by the NASA Goddard Space Flight Center.
We present current and near-term uses of high-power fiber lasers and amplifiers for NASA science and spacecraft
applications. Fiber lasers and amplifiers offer numerous advantages for the deployment of instruments on exploration
and science remote sensing satellites. Ground-based and airborne systems provide an evolutionary path to space and a
means for calibration and verification of space-borne systems. NASA fiber-laser-based instruments include laser
sounders and lidars for measuring atmospheric carbon dioxide, oxygen, water vapor and methane and a pulsed or
pseudo-noise (PN) code laser ranging system in the near infrared (NIR) wavelength band. The associated fiber
transmitters include high-power erbium, ytterbium, and neodymium systems and a fiber laser pumped optical parametric
oscillator. We discuss recent experimental progress on these systems and instrument prototypes for ongoing
At NASA's Goddard Space Flight Center we are developing next generation laser transmitters for future spaceflight,
remote instruments including a micropulse altimeter for ice-sheet and sea ice monitoring, laser spectroscopic
measurements of atmospheric CO2 and an imaging lidar for high resolution mapping of the Earth's surface. These laser
transmitters also have applicability to potential missions to other solar-system bodies for trace gas measurements and
surface mapping. In this paper we review NASA spaceflight laser transmitters used to acquire measurements in orbit
around Mars, Mercury, Earth and the Moon. We then present an overview of our current spaceflight laser programs and
describe their intended uses for remote sensing science and exploration applications.
At NASA's Goddard Space Flight Center, we are developing the next generation laser transmitters for future remote
sensing applications including a micropulse altimeter for ice-sheet monitoring, laser spectroscopic measurements and
high resolution mapping of the Earth's surface as well as potential missions to other planets for trace gas measurement
and mapping. In this paper we will present an overview of the spaceborne laser programs and offer insights into future
spaceborne lasers for remote sensing applications.
In several future space telescope missions, high long-term relative stability between optics is required for testing on the
ground, as well as achieving the sensitivity goal in flight. Typically, thermal and seismic drifts on the ground are on the
order of 1 μm over few hours, orders of magnitude above the testing requirements. To suppress these environmental
motions, we developed a control system that is composed of interferometric sensors and PZT-based actuator. The system
provides a stable environment to allow ground testing of the mission requirements. Our results show that this kind of
system can provide picometer level stability at long timescale and that it should have many applications.
A number of future space observatories will rely on interferometric length measurements to meet mission requirements. A necessary tool for these measurements is a frequency stabilized laser. We present the use of molecular resonances for the frequency stabilization reference for the TPF-C, LISA, and MAXIM missions. For the TPF-C terrestrial planet finder coronagraph mission we have stabilized a 1542nm fiber laser to acetylene and exceeded the required sensitivity for length measurements of less than 25nm over a length scale of 12m and a time scale of 8 hours. For the LISA gravitational wave interferometer mission we have stabilized a frequency doubled 1064nm NPRO laser to molecular iodine. The laser system meets the frequency noise requirements of 30Hz/√(Hz) at mHz frequencies and shows robustness to temperature and alignment fluctuations. It also supplies an absolute reference frequency which is important for lock acquisition of lasers on separate spacecraft. The radiation hardness of the frequency doubling crystal for iodine stabilization was studied. In addition, simplified optical configurations have also been investigated, where the need for auxiliary modulators was eliminated. For MAXIM, we have constructed a stabilized laser system for stabilization of the position of the x-ray optics in the GSFC prototype testbed, and we report some initial results in the testbed operation.
The LIGO project has completed the installation of large fused silica optical components in the vacuum systems of its observatories. Commissioning work on the Hanford 2 km interferometer has determined an upper limit to the optics losses, allowing comparison with design and pre-installation testing. Planning and development of sapphire optics for the next generation, advanced LIGO detector is now underway, including polishability, optical homogeneity, absorption, and birefringence. The advanced optics development also includes research aimed at lowering coating loss.
In order to improve the detection sensitivity of the Laser Interferometer Gravitational-wave Observatory (LIGO) the use of 40-kg sapphire test masses is being considered for the next instrument upgrade. Currently, sapphire material of adequate size is only available with the optical axis aligned with the m axis of the crystal. To determine the material's suitability it is necessary to characterize the refractive index inhomogeneity of the sapphire substrates for two orthogonal directions of polarisation, to a fraction of a part per million (ppm). We report on a method used to measure the refractive index inhomogeneity which requires three separate measurements of the polished sapphire blank in a Fizeau interferometer. These measurements are of the surface shapes or figures of the two polished sides of the blank and that of the wavefront entering side one propagating through the blank, reflected off side two and exiting through side one. The phase maps corresponding to these three measurements are combined to obtain the refractive index inhomogeneity map distribution. Measurements were carried out on two sapphire substrates (m axis) produced by the heat exchange method. The inhomogeneity maps show features which depend on polarisation direction. The physical origin of the inhomogeneities is discussed as well as the probable impact on the detection of a gravitational wave signal.