Television – Special applications – Observation of or from a specific location
Reexamination Certificate
2001-05-21
2001-12-18
Britton, Howard (Department: 2613)
Television
Special applications
Observation of or from a specific location
C348S208400, C348S211130
Reexamination Certificate
active
06331870
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods and systems for making global observations of the Earth at sub-kilometer spatial resolutions in real-time, where real-time refers to a delay of not more than two minutes total for creating, refreshing and distributing each image. More particularly, the present invention is directed towards methods, apparatuses and systems that provide real-time coverage of at least 70% of the observable Earth surface at a spatial resolution of less than 1 kilometer.
2. Discussion of the Background
Over the last 30 years, since the first weather monitoring satellite was placed in geostationary earth orbit (GEO), various satellite systems have been used to monitor features of the Earth. The reason is that at GEO the relative motion of the Earth and the satellite is nulled, provided that the GEO orbit is in the Earth's equatorial plane. Accordingly, consistent images may be taken of the portion of the Earth's surface and atmosphere that fall within the footprint of the satellite.
In the Western hemisphere, weather forecasting methods rely heavily on data supplied by the Geostationary Operational Environmental Satellites (GOES) series, operated by the National Oceanic and Atmospheric Administration (NOAA). The GOES series was developed from the prototype “Advanced Technology Systems” 1 and 3 (ATS-1, -3) launched in 1966 and 1967, respectively. These and all subsequent systems have been implemented with scanning imaging systems that are able to produce full disk images of the Earth at 1 km resolution in about 20-30 minutes.
The newest of the GOES satellites (
8
,
9
and
10
) are 3-axis stabilized and are configured to observe the Earth with 1 panchromatic visible and 4 infrared imaging systems per satellite. The visible imaging systems use a “flying spot” scanning technique when a mirror moving in two axes, East-West and North-South, scans a small vertically oriented element of the fully viewable scene (the instrument's full area of regard) across an array of eight vertically arranged silicon pixels. The individual pixel field of view is about 30 &mgr;rad. Each scene element is sampled for just under 50 microseconds. In order to support this slow scanning method, the GOES satellite payload stability must be extraordinarily high so that almost no relative movement occurs between any one scan line of the samples. Accordingly, the payload pointing does not nominally deviate further than ⅓ of a pixel during an entire, 1 second duration scan. Because there are over 1,300 scan lines to create a full disk image it takes about 22 minutes to create the full image. Operationally, a full disk sampling technique is actually done once every three hours, to allow more frequent coverage of an entire visible hemisphere rather than a more frequent sampling of smaller regions.
During normal operation, GOES series satellites provide gray-scale and infrared images of different portions of the Earth at between 5, 15 and 30 minute intervals. Limited regions may be sampled as frequently as about once per minute, during “super rapid scan operations” (SRSO). In practice, SRSO operations are rarely used because coverage of other areas is too important to be neglected for long periods of time. Moreover, significant Earth-based events that occur during lapses in coverage of a particular region may be missed. In other words, the satellites sensor may be looking an uneventful portion of the Earth's surface when the significant activity is occurring at another portion of the Earth's surface. Furthermore, as recognized by the present inventor, phenomena that may occur at night can only be seen in the infrared channels, which have a much coarser spatial resolution than the visible channel and otherwise are subject to the same limitations that are inherent in a scanning system.
GOES satellites provide a system that is optimized for monitoring cloud motion, but is far less suitable for observing other GEO physical events. At visible wavelengths, clouds are efficient diffuse mirrors of solar radiation and therefore appear white with variations of brightness seen as shades of gray. Color, enhancing the contrast and visibility of the Earth's surface background, may actually detract from cloud visibility in a scene. Moreover, adding color may triple the amount of information and thus size of a digitized image, which creates a burden on the transmission demands for the broadcast portion of the satellite system. Furthermore, observations of significant, but perhaps transient phenomena that occur in time scales of seconds or minutes (such as volcanoes, lightening strikes or meteors) may be late or not observed at all. Accordingly, the information provided from systems like the GOES system is somewhat unreliable because it is not able to provide a high-resolution “watchdog” service that reliably reports real-time information over a significant portion of the Earth's surface. Also, “video” style loops created from successive images having relatively coarse temporal resolution may lack the continuity needed to provide truly reliable information if cloud movements between image samples are much greater than a pixel dimension. The temporal coherence among the pixels of a scanned image and between the co-registered pixels of successive images will degrade as the time required to create the image and the elapsed time interval between scans increases. These effects have a significant adverse impact on the fidelity of any “image” created to represent the state of the Earth at a given moment, but particularly harmful to attempts to build animations using successive co-registered scanned images of a given area.
Referring to
FIG. 1
, coverage area are shown for various weather satellites in addition to the GOES satellites. The GMS-5, parked at 140° East longitude, is a Japanese weather satellite showing a coverage area that covers the South-East Asia and Australian areas of the world. The Chinese FY (Feng-Yang) satellite is parked at 104° East and shows a substantially overlapping coverage area with the GMS-5 satellite. The European space agency's METEOSTAT-6 satellite, parked in a 0° orbit, requires a license to decrypt and thus limits distribution for three days after observation. In contrast, the GOES, GMS and FY satellites have open reception and distribution via NASA-funded Internet links. Other satellites that perform similar operation include the Indian INSAT-1D, which is parked at 74° East longitude, and the Russian system, GOMS/ELECTRO, which is not currently operational. A common feature of these different satellite systems is that they employ a spin scan or scanning visible imaging systems that require up to 20 minutes or longer to acquire a full disk image of the Earth. Furthermore, the systems use the long scan period to provide a variety of spatial resolutions, but all of which are more coarse than 1 km at the Nadir point.
There have been a number of proposals made in the past by various individuals and groups to place a camera on a large commercial communication satellite positioned in GEO. In each case, the camera would operate as a parasitic device, in that the camera would use the power and communication sub-system of the satellite to support its operational requirements. The most recent and most detailed examples, were made by Hughes Information Technology Corporation, a former subsidiary of Hughes Aircraft Company and the MITRE Corporation. These examples are discussed below.
The Hughes Proposal was described under various names such as “EarthCam”, “StormCam”, and “GEM” (Geostationary Earth Monitor) and involved a television style imaging system using a two dimensional charge coupled device (CCD) detector array to create an image of 756 pixels wide by 484 pixels high at intervals that range from between two minutes to eight minutes. The frame rate for this TV-style camera was determined by compression limitations in the satellite's meager 1-5 Kbps housekeeping data channel capacity.
AstroVision, Inc.
Britton Howard
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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