Thomas Humpherys

Melting points of gallium and of binary eutectics with gallium realized in small cells

Melting/freezing curves are studied for the single-component Ga and bimetallic eutectic alloys Ga–In, Ga–Sn, Ga–Zn and Ga–Al in small-size cells. These phase-transition studies were conducted at VNIIOFI and SDL in order to design small-size fixed-point devices for metrological monitoring of temperature sensors on autonomous platforms. Our prime objective is to develop technology to improve the long-term performance of in-flight blackbody calibration sources of space-borne radiometers. The repeatability of the melting temperature of Ga and the eutectic melting temperatures of Ga–In, Ga–Sn and Ga–Zn fixed points were studied. Our results show that small cells containing Ga and some Ga-based eutectic alloys can be used as melting fixed-point standards.

The Global Earth Observation System of Systems (GEOSS) and metrological support for measuring radiometric properties of objects of observations

The international Global Earth Observation System of Systems is at its initial stage. We present some general information about the program and formulate the task of ensuring the uniformity of radiometric measurements to be conducted by all the participating national systems. Methods of solving the task are suggested on the basis of the wide application of standard sources that use phase transition of eutectic alloys and pure metals as well as with the help of improved ground calibration facilities.

Metrological support for climatic time series of satellite radiometric data

A necessary condition for accumulating fundamental climate data records is the use of observation instruments whose stability and accuracy are sufficiently high for climate monitoring purposes; the number of instruments and their distribution in space should be sufficient for measurements with no spatial or temporal gaps. The continuous acquirement of data over time intervals of several decades can only be possible under the condition of simultaneous application of instruments produced by different manufacturers and installed on different platforms belonging to one or several countries. The design of standard sources for pre-flight calibrations and in-flight monitoring of instruments has to meet the most stringent requirements for the accuracy of absolute radiometric measurements and stability of all instruments. This means that the radiometric scales should be stable, accurate, and uniform. Current technologies cannot ensure the high requirements for stability and compatibility of radiometric scales: 0.1% per decade within the 0.3 - 3 μm band and 0.01 K per decade within the 3 - 25 μm band. It is suggested that these tasks can be aided through the use of the pure metals or eutectic alloy phase transition phenomenon that always occur under the same temperature. Such devices can be used for pre-flight calibrations and for on-board monitoring of the stability of radiometric instruments. Results of previous studies of blackbody models based upon the phase transition phenomenon are quite promising. A study of the phase transition of some materials in small cells was conducted for future application in onboard monitoring devices and its results are positive and allow us to begin preparations for similar experiments in space.

Sensor design and capabilities for the Russian American Observational Satellites (RAMOS)

RAMOS, the Russian American Observational Satellite program, is a cooperative space-based research and development program between the Russian Federation and the United States. The planned system configuration is a constellation of two satellites orbiting in approximately the same plane at an altitude of about 500 km, separated from one another by a variable distance centering on about 500 km. These satellites are equipped with passive electro-optical sensors, both US- and Russian-built, that operate over a range from infrared (IR) to ultraviolet (UV) and are designed for near-simultaneous stereo imaging capability. The sensor suite will include visible, IR and UV imaging radiometers, an IR spectrometer, and a short-wave infrared (SWIR) polarimeter. The projected launch date is 2008 with a planned minimum on-orbit lifetime of two years, and a five-year lifetime possible. This paper summarizes the program objectives, anticipated measurements and expected data, and presents the basic system design, expected performance characteristics, and the capabilities of each of the sensors.

Environmental objectives for the Russian American Observational Satellites (RAMOS)

The RAMOS program embodies a new direction for cooperative space-based cooperative research and development between the Russian Federation and the United States. The planned system configuration is a constellation of two satellite constellation orbiting in approximately in the same plane and at an altitude of about 500 km. These satellites, equipped with passive electro-optical sensors operating from infrared (IR) to ultraviolet (UV), are designed for near-simultaneous stereo-optical measurement capability. The projected launch date is 2007 with an on-orbit lifetime of two years minimum and five years possible. The environmental objectives are: 1. Measuring cyclones to predict their future strengths and paths, 2. Measuring fires and winds to demonstrate location and assessment capability, 3. Measuring volcanic plumes in three dimensions 3-D measurements of volcanic plumes for to assess aircraft hazards, 4. Measuring global three-dimensional wind velocities, 5. Measuring water vapor profiles at the 100-meter scale, 6. Obtaining a three-dimensional multi-spectral background data base in the mid-wave infrared, visible and ultraviolet wavelength regions and making infrared and visible polarization measurements of solar scattered backgrounds.

Utilizing UV and visible sensors on micro-satellites to demonstrate target acquisition and tracking

The Distributed Sensing Experiment (DSE) program is a technology demonstration of target acquisition, tracking, and three-dimensional track development using a constellation of three micro satellites. DSE will demonstrate how micro satellites, working singly and as a group, can observe test-missile boost and ballistic-flight events. The overarching program objective is to demonstrate a means of fusing measurements from multiple sensors into a composite track. To perform this demonstration, each DSE micro satellite will acquire and track a target, determine a two-dimensional direction and movement rate for each, communicate observations to other DSE satellites, determine a three-dimensional target position and velocity, and relay this information to ground systems. A key design parameter of the program is incorporating commercial off-the-shelf (COTS) hardware and software to reduce risk and control costs, while maintaining performance. Having completed a successful Critical Design Review, the program is currently in fabrication, integration, and test phase. The constellation of satellites is scheduled for launch in CY2009. This paper describes the status and capabilities of the UV and visible sensor payloads, as well as the algorithms and software being developed to achieve the DSE mission.

New generation of space capabilities resulting from US/RF cooperative efforts

Previous successful international cooperative efforts offer a wealth of experience in dealing with highly sensitive issues, but cooperative remote sensing for monitoring and understanding the global environmental is in the national interest of all countries. Cooperation between international partners is paramount, particularly with the Russian Federation, due to its technological maturity and strategic political and geographical position in the world. Based on experience gained over a decade of collaborative space research efforts, continued cooperation provides an achievable goal as well as understanding the fabric of our coexistence. Past cooperative space research efforts demonstrate the ability of the US and Russian Federation to develop a framework for cooperation, working together on a complex, state-of-the-art joint satellite program. These efforts consisted of teams of scientists and engineers who overcame numerous cultural, linguistic, engineering approaches and different political environments. Among these major achievements are: (1) field measurement activities with US satellites MSTI and MSX and the Russian RESURS-1 satellite, as well as the joint experimental use of the US FISTA aircraft; (2) successful joint Science, Conceptual and Preliminary Design Reviews; (3) joint publications of scientific research technical papers, (4) Russian investment in development, demonstration and operation of the Monitor-E spacecraft (Yacht satellite bus), (5) successful demonstration of the conversion of the SS-19 into a satellite launch system, and (6) negotiation of contractual and technical assistant agreements. This paper discusses a new generation of science and space capabilities available to the Remote Sensing community. Specific topics include: joint requirements definition process and work allocation for hardware and responsibility for software development; the function, description and status of Russian contributions in providing space component prototypes and test articles; summary of planned experimental measurements and simulations; results of the ROKOT launch system; performance of the Monitor-E spacecraft; prototype joint mission operations control center; and a Handbook for Success in satellite collaborative efforts based upon a decade of lessons learned.

The Space Metrology Program

The full potential of current remote sensor technology is limited by the inability to correct biases once an exo-atmospheric remote sensor becomes operational. Even when the calibration is traced to the International System of Units, SI, and the instrument is performing within the operational envelope wherein it is calibrated, the problem exists and a Space Metrology Program is a potential solution to the problem. This paper discusses such a program, suggests a feasibility study to address the issues and recommends a plan of action. Any operational instrument has a bias and reducing the magnitude of the bias can only be accomplished when an adequately accurate standard is accessible by the instrument while the instrument is in its operational environment. Currently the radiometric flux from the sun, the moon and the stars is inadequately accurate SI to provide a standard that is consistent with the remote sensor state-of-the-art technology. The result is data that is less accurate than it could be often leading to confusing and conflicting conclusions drawn from that data. Planned remote sensors such as those required to meet future program needs (e.g. the United States National Polar-Orbiting Operational Environmental Satellite System (NPOESS) and the proposed international Global Earth Observation Program) are going to need the higher accuracy radiometric standards to maintain their accuracy once they become operational. To resolve the problem, a set of standard radiometers on the International Space Station is suggested against which other exo-atmospheric radiometric instruments can be calibrated. A feasibility study for this program is planned.