William T. Roberts

LLCD operations using the Optical Communications Telescope Laboratory (OCTL)

The Optical Communications Telescope Laboratory (OCTL) located on Table Mountain near Wrightwood, CA served as an alternate ground terminal to the Lunar Laser Communications Demonstration (LLCD), the first free-space laser communication demonstration from lunar distances. The Lunar Lasercom OCTL Terminal (LLOT) Project utilized the existing 1m diameter OCTL telescope by retrofitting: (i) a multi-beam 1568 nm laser beacon transmitter; (ii) a tungsten silicide (WSi) superconducting nanowire single photon detector (SNSPD) receiver for 1550 nm downlink; (iii) a telescope control system with the functionality required for laser communication operations; and (iv) a secure network connection to the Lunar Lasercom Operations Center (LLOC) located at the Lincoln Laboratory, Massachusetts Institute of Technology (LL-MIT). The laser beacon transmitted from Table Mountain was acquired by the Lunar Lasercom Space Terminal (LLST) on-board the Lunar Atmospheric Dust Environment Explorer (LADEE) spacecraft and a 1550 nm downlink at 39 and 78 Mb/s was returned to LLOT. Link operations were coordinated by LLOC. During October and November of 2013, twenty successful links were accomplished under diverse conditions. In this paper, a brief system level description of LLOT along with the concept of operations and selected results are presented.

Preliminary Results of the OCTL to OICETS Optical Link Experiment (OTOOLE)

JPL in collaboration with JAXA and NICT demonstrated a 50Mb/s downlink and 2Mb/s uplink bi-directional link with the LEO OICETS satellite. The experiments were conducted in May and June over a variety of atmospheric conditions. Bit error rates of 10-1 to less than 10-6 were measured on the downlink. This paper describes the preparations, precursor experiments, and operations for the link. It also presents the analyzed downlink data results.

Development of laser beam transmission strategies for future ground-to-space optical communications

Optical communications is a key technology to meet the bandwidth expansion required in the global information grid. High bandwidth bi-directional links between sub-orbital platforms and ground and space terminals can provide a seamless interconnectivity for rapid return of critical data to analysts. The JPL Optical Communications Telescope Laboratory (OCTL) is located in Wrightwood California at an altitude of 2.2.km. This 200 sq-m facility houses a state-of- the-art 1-m telescope and is used to develop operational strategies for ground-to-space laser beam propagation that include safe beam transmission through navigable air space, adaptive optics correction and multi-beam scintillation mitigation, and line of sight optical attenuation monitoring. JPL has received authorization from international satellite owners to transmit laser beams to more than twenty retro-reflecting satellites. This paper presents recent progress in the development of these operational strategies tested by narrow laser beam transmissions from the OCTL to retro-reflecting satellites. We present experimental results and compare our measurements with predicted performance for a variety of atmospheric conditions.

Deep-space optical terminals (DOT)

A conceptual design study titled Deep-space Optical Terminals was recently completed for an optical communication technology demonstration from Mars in the 2018 time frame. We report on engineering trades for the entire system, and for individual subsystems including the flight terminal, the ground receiver and the ground transmitter. A point design is described to meet the requirement for greater than 0.25 Gb/s downlink from the nearest distance to Mars of 0.42 AU with a maximum mass and power allocation of 40 kg and 110 W. Furthermore, the concept design addresses link closure at the farthest Mars range of 2.7 AU. Maximum uplink data-rate of 0.3 Mb/s and ranging with 30 cm precision are also addressed.

Turning Palomar into a deep-space optical receiver

The approach for adapting the 200-inch Hale telescope, located at Mt. Palomar, CA to support a deep space optical communications project is outlined. Considerations include protecting the telescope for daytime operations and limiting the amount of background detected by the receiver.

A bidirectional low Earth orbit-to-ground optical link experiment

Free-space optical communications using existing space-borne assets is a cost-effective way to show the maturity of the technology for future missions. To this end, NASA’s Jet Propulsion Laboratory (JPL) undertook a joint experiment with the Japanese Aerospace Exploration Agency to perform a bidirectional optical link between the Laser Utilizing Communication Experiment (LUCE) instrument run by the National Institute of Information and Communications Technology on the Optical Inter-orbit Communications Experiment Test Satellite (OICETS)1 and the JPL Optical Communications Telescope Laboratory (OCTL) 1m ground station (see Figure 1). Originally tasked for intersatellite communications with the geostationary earth orbit (GEO) Artemis spacecraft that were successfully completed in 2006, the low-Earth-orbit (LEO) OICETS also supported space-to-ground links by inverting the spacecraft and pointing LUCE towards the ground using onboard gyros, providing navigation for extended periods of time. There were several objectives for OTOOLE (OCTL-To-OICETS Optical Link Experiment). First, the experiment aimed to demonstrate acquisition and tracking of a LEO satellite from the OCTL and perform an optical communications link with 2Mb/s uplink and 50Mb/s downlink. Second, it sought to validate operational issues to support an optical communications link, such as link models and aperture-averaging effects. And finally, the experiment hoped to characterize link performance for a variety of atmospheric and background conditions. The campaign began in January 2009 and quickly completed four successful link demonstrations at each attempt in May and June 2009.2 Experiment windows occurred between 3 and Figure 1. The Jet Propulsion Laboratory (JPL) OTOOLE (OCTLTo-OICETS Optical Link Experiment) between the JPL ground station and the Japanese Aerospace Exploration Agency satellite. OCTL: Optical Communications Telescope Laboratory. OICETS: Optical Inter-orbit Communications Experiment Test Satellite. BPPM and OOK are data-modulation formats.

Data Products for the OCTL to OICETS Optical Link Experiment

JPL has developed a series of software and hardware tools to analyze and record data from a 50Mb/s down and 2 Mb/s up bi-directional optical link with the LUCE terminal onboard the LEO OICETS satellite. This paper presents the data products for this experiment including the system architecture and analysis of the actual data received.

Deep-space optical terminals: Ground laser receiver

Deep-space Optical Terminals (DOT) is a concept for providing bi-directional communication between a spacecraft at planetary distances and ground. The objective is a system that delivers 10 times the data-rate of a state-of-the-art Ka-band system while putting a comparable mass and power burden on the spacecraft. Here we give an overview of the concept for the Ground Laser Receiver (GLR) terminal. We discuss the selection of telescopes, receiver optics, detectors, and electronics.

The advanced solar observatory

We describe a conceptual plan for the development of a comprehensive long duration solar space observatory, the Advanced Solar Observatory (ASO). The ASO is intended to provide solar astronomers with the observational power (spectral, spatial, and temporal resolution, sensitivity, and breadth of wavelength coverage) necessary to address fundamental problems relating to the solar convection zone and activity cycle, the thermal and nonthermal processes that control the transport of energy, mass, and magnetic flux in the solar atmosphere, the generation of the solar wind, and the dynamics of the inner heliosphere. The ASO concept encompasses three proposed space station based instrument ensembles: (i) the High Resolution Telescope Cluster, which includes far ultraviolet, extreme ultraviolet, and x-ray telescopes, (ii) the Pinhole/Occulter Facility, which includes Fourier transform and coded aperture hard x-ray and gamma ray telescopes and occulted ultraviolet and visible light coronagraphs, and (iii) the High Energy Facility, which contains neutron, gamma ray, and low frequency radio spectrometers. Two other facilities, the Orbiting Solar Laboratory, which will contain high resolution visible and ultraviolet telescopes on a free-flying platform, and a package of Global Dynamics Instrumentation will, with the space station ensembles, form a comprehensive capability for solar physics. We describe the scientific program of the ASO, current instrument concepts for the space station based ASO instrument ensembles, and plans for their accommodation on the space station.

Overview of Ground Station 1 of the NASA space communications and navigation program

Optical Ground Station 1 (OGS1) is the first of a new breed of dedicated ground terminals to support NASA’s developing space-based optical communications infrastructure. It is based at NASA’s Optical Communications Telescope Laboratory (OCTL) at the Table Mountain Observatory near Wrightwood, CA. The system will serve as the primary ground station for NASA’s Laser Communications Relay Demonstration (LCRD) experiment. This paper presents an overview of the OCTL telescope facility, the OGS1 ground-based optical communications systems, and the networking and control infrastructure currently under development. The OGS1 laser safety systems and atmospheric monitoring systems are also briefly described.