Multifrequency Aperture-Synthesizing Microwave Radiometer System (MFASMR). Volume 1

Background material and a systems analysis of a multifrequency aperture - synthesizing microwave radiometer system is presented. It was found that the system does not exhibit high performance because much of the available thermal power is not used in the construction of the image and because the image that can be formed has a resolution of only ten lines. An analysis of image reconstruction is given. The system is compared with conventional aperture synthesis systems

Application of advanced technology to space automation

Automated operations in space provide the key to optimized mission design and data acquisition at minimum cost for the future. The results of this study strongly accentuate this statement and should provide further incentive for immediate development of specific automtion technology as defined herein. Essential automation technology requirements were identified for future programs. The study was undertaken to address the future role of automation in the space program, the potential benefits to be derived, and the technology efforts that should be directed toward obtaining these benefits

Passive Millimeter-Wave Imaging Based on Subharmonic Self-Oscillating Mixing

RÉSUMÉ Le sujet général de la thèse de doctorat présentée réside dans la recherche sur des nouvelles méthodes dans le domaine de l’imagerie aux micro-ondes, en particulier l’imagerie passive aux ondes millimétriques, qui est aussi connue sous le nom d’imagerie radiométrique. Cette dernière technique est utilisée pour former une image d’une scène particulière en capturant la radiation électromagnétique émise naturellement par chaque objet à la bande de fréquence des micro-ondes / ondes millimétriques, similaire à la façon dont une photographie est prise en capturant la radiation aux fréquences optiques. De cette façon, une image d’ondes millimétriques peut être formée et utilisée pour tracer différentes caractéristiques de la scène ou de l’objet, qui sont implicites à la bande de fréquences des micro-ondes / ondes millimétriques. L’imagerie à ondes millimétriques représente un des sujets d’actualité des plus prometteurs dans le domaine de la conception des capteurs à haute fréquence. L’utilité de cette technique réside surtout dans les particularités des phénomènes de l’atténuation atmosphérique permettant aux ondes millimétriques de pénétrer à travers une grande variété de conditions de mauvaise visibilité, comme par exemple la brume, le brouillard, les nuages, la fumée et les tempêtes de sable, ainsi que la capacité de se propager à travers des vêtements et certains autres matériaux. Outre ces avantages par rapport aux systèmes infrarouges ou optiques, les systèmes à ondes millimétriques surpassent les systèmes micro-ondes à plus basse fréquence par leurs longueurs d’ondes plus petites permettant d’atteindre une plus haute résolution. Pour leur mise en application, des fenêtres de propagation à 35, 77, 94, 140 et 220 GHz ont été assignées. Les domaines d’application présents et futurs sont principalement associés aux infrastructures militaires et commerciales. Ceux-ci englobent la surveillance, la navigation et la technologie automobile, ainsi que l’atterrissage des avions et le suivi de la circulation dans le brouillard sur les autoroutes. De plus, la demande de plus en plus grande en systèmes de détection de sécurité aux aéroports et d’autres lieux publics crée une demande toujours plus grande en scanners automatisés en temps réel dotés des caractéristiques suivantes : ne présenter aucun risque pour la santé, générer un nombre réduit de fausses alertes et permettre la détection des armes cachées ou des objets dangereux à travers les vêtements.----------ABSTRACT The broad topic of the presented Ph.D. thesis consists in the research on novel methods in the field of microwave imaging, in particular the so-called passive millimetre-wave imaging, which is also referred to as radiometric imaging. This latter technique is used to form an image of a particular scene by means of sensing the natural electromagnetic radiation emitted by any object at microwave / millimetre-wave wavelengths, similar to the way in which a photograph is captured by sensing the radiation occurring at optical wavelengths. In this way, different characteristics of the observed scene or object, which are inherent to the microwave / millimetre-wave frequency range, can be mapped in the form of an image. Millimetre-wave imaging represents one of today’s most promising research topics in the field of high frequency sensor design. The usefulness of this technique lies in particular in the peculiarities of atmospheric attenuation phenomenologies allowing millimetre-waves to penetrate through a variety of low-visibility conditions such as haze, fog, clouds, smoke, and sandstorms and furthermore in the ability to propagate through clothing and a number of other materials. Together with these advantages over infrared and optical systems, moreover, millimetre-wave systems outperform imagers at the lower microwave frequency range due to their smaller wavelengths and the thus achievable higher resolution. For their implementation, propagation windows at 35, 77, 94, 140, and 220 GHz are generally allocated. Present and future applications consist in both military and commercial infrastructure fields such as in surveillance, navigation, and automotive technology, as well as aircraft landing or highway traffic monitoring in fog. Moreover, the ever increasing demand for security screening systems at airports and other public environments creates a growing need for health-hazardless automated real-time scanners with minimized false alarms, and millimetre-wave imaging offering the ability to detect concealed weapons or hazardous objects through clothing material represents an excellent choice for this purpose. Furthermore, millimetre-wave imaging is applied to biomedical imaging such as the location of hot spots, tumours, or other anomalies in the body. Additional applications consist in non-destructive material testing and geological examinations such as the sensing of the Earth’s atmosphere, oil spill detection, research on volcano activity, or meteorology

Study of spacecraft direct readout meteorological systems

Characteristics are defined of the next generation direct readout meteorological satellite system with particular application to Tiros N. Both space and ground systems are included. The recommended space system is composed of four geosynchronous satellites and two low altitude satellites in sun-synchronous orbit. The goesynchronous satellites transmit to direct readout ground stations via a shared S-band link, relayed FOFAX satellite cloud cover pictures (visible and infrared) and weather charts (WEFAX). Basic sensor data is transmitted to regional Data Utilization Stations via the same S-band link. Basic sensor data consists of 0.5 n.m. sub-point resolution data in the 0.55 - 0.7 micron spectral region, and 4.0 n.m. resolution data in the 10.5 - 12.6 micron spectral region. The two low altitude satellites in sun-synchronous orbit provide data to direct readout ground stations via a 137 MHz link, a 400 Mhz link, and an S-band link

Sensitivity and noise in THz electro-optic upconversion radiometers

This paper presents a study of noise in room-temperature THz radiometers that use THz-to-optical upconversion followed by optical detection of thermal radiation. Despite some undesired upconverted thermal noise, no noise is intrinsically introduced by efcient electro-optic modulation via a sumfrequency-generation process in high quality factor (Q) whispering-gallery mode (WGM) resonators. However, coherent and incoherent optical detection results in fundamentally diferent noise characteristics. The analysis shows that the upconversion receiver is quantum limited like conventional amplifers and mixers, only when optical homodyne or heterodyne detection is performed. However, this type of receiver shows advantages as a THz photon counter, where counting is in the optical domain. Theoretical predictions show that upconversion-based room-temperature receivers can outperform state-of-the-art cooled and room-temperature THz receivers based on low-noise amplifers and mixers, provided that a photon conversion efciency greater than 1% is realized. Although the detection bandwidth is naturally narrow due to the highly resonant electro-optic modulator, it is not fundamentally limited and can be broadened by engineering selective optical coupling mechanisms to the resonator.Ministerio de Economía y Competitividad (MINECO) (TEC2013-47753-C3); Comunidad de Madrid MARTINLARA Project (ref. P2018/NMT-4333); FUNDACION SENER; Banco Santander (TEC2016-76997- C3-2-R); 2017 UC3M-Santander Chair of Excellence

A 3.5-THz, x6-Harmonic, Single-Ended Schottky Diode Mixer for Frequency Stabilization of Quantum-Cascade Lasers

Efficient and compact frequency converters are essential for frequency stabilization of terahertz sources. In this paper, we present a 3.5-THz, x6-harmonic, integrated Schottky diode mixer operating at room temperature. The designed frequency converter is based on a single-ended, planar Schottky diode with a sub-micron anode contact area defined on a suspended 2-$\mu$m ultra-thin GaAs substrate. The dc-grounded anode pad was combined with the radio frequency E-plane probe, which resulted in an electrically compact circuit. At 200 MHz intermediate frequency, a mixer conversion loss of about 59 dB is measured and resulting in a 40 dB signal-to-noise ratio for phase locking 3.5-THz quantum-cascade laser. Using a quasi-static diode model combined with electromagnetic simulations, good agreement with the measured results was obtained. Harmonic frequency converters without the need of cryogenic cooling will help in the realization of highly sensitive space and air-borne heterodyne receivers.Comment: Submitted to IEEE-TS

Indoor Full-Body Security Screening: Radiometric Microwave Imaging Phenomenology and Polarimetric Scene Simulation

The paper discusses the scene simulation of radiometric imagers and its use to illustrate the phenomenology of full-body screening of people for weapons and threats concealed under clothing. The aperture synthesis technique is introduced as this offers benefits of wide field-of-views and large depths-of-fields in a system that is potentially conformally deployable in the confined spaces of building entrances and at airport departure lounges. The technique offers a non-invasive, non-cooperative screening capability to scrutinize all human body surfaces for illegal items. However, for indoor operation, the realization of this capability is challenging due to the low radiation temperature contrasts in imagery. The contrast is quantified using a polarimetric radiometric layer model of the clothed human subject concealing threats. A radiation frequency of 20 GHz was chosen for the simulation as system component costs here are relatively low and the attainable half-wavelength spatial resolution of 7.5 mm is sufficient for screening. The contrasts against the human body of the threat materials of metal, zirconia ceramic, carbon fiber, nitrogen-based energetic materials, yellow beeswax, and water were calculated to be ≤7 K. Furthermore, the model indicates how some threats frequency modulate the radiation temperatures by ~ ±1 K. These results are confirmed by experiments using a radiometer measuring left-hand circularly polarized radiation. It is also shown using scene simulation how circularly polarized radiation has benefits for reducing false alarms and how threat objects appear in canyon regions of the body, such as between the legs and in the armpits

Coastal-zone oceanographic requirements for earth observatory satellites A and B, part 1 Final report

Coastal zone oceanographic requirements for earth observatory satellites - Part

Remote sensing in the coastal and marine environment. Proceedings of the US North Atlantic Regional Workshop

Presentations were grouped in the following categories: (1) a technical orientation of Earth resources remote sensing including data sources and processing; (2) a review of the present status of remote sensing technology applicable to the coastal and marine environment; (3) a description of data and information needs of selected coastal and marine activities; and (4) an outline of plans for marine monitoring systems for the east coast and a concept for an east coast remote sensing facility. Also discussed were user needs and remote sensing potentials in the areas of coastal processes and management, commercial and recreational fisheries, and marine physical processes