Форум » Дискуссии » synthetic apperture radar » Ответить
synthetic apperture radar
milstar: Nize priwedenni primeri image i movie s dowolno wisokoj razreschajuschej sposobnost'ju 100 mm dlja SAR radara w diapazonax Ka(35ghz) i Ku waznejschij wopros dlja kakoj wojni . ######################## S-300 imelo porjadka 1500 yabch . W yslowijax podriwa serii yabch w atmosfere wse eto s xoroschim chansom ne budet rabotat' Bolee wisokuju boewuju ystojchiwost' budut imet' multimegawattnie rls s bolschoj apperturoj na lampax http://www.sandia.gov/RADAR/imageryka.html kollekzija image ot 35 ghz synthetic apperture radar razr.sposobnost' 4 inches -10 sm,100 millimetr Contact: To send feedback or request information about the contents of Sandia National Laboratories' synthetic aperture radar website, please contact: Nikki L. Angus Synthetic Aperture Radar Website Owner Sandia National Laboratories Albuquerque, NM 87185-1330 (505) 844-7776 (Phone) (505) 845-5491 (Fax) nlangus@sandia.gov http://www.sandia.gov/RADAR/movies.html kollekzija video s SAR Ku band i raz sposb 300 mm
milstar: Radar performance degrades in environments disturbed by nuclear explosions. ################################################### Hit- to-kill GBIs eliminate the nuclear weapon in the interceptor, but not that in the incoming RV, which could detonate on contact or command. ####################################### Neskolko yglow attaki ,na kazdom formazija/gruppirowka po 100 -1000 boegolowok W ochen' xoroschim/xoroschim chansom chast' iz nix budet podorwanna po prodwizeniju k rajonu attaki dlja degradazii/polnoj newozmoznosti funkzionirowanija rls PRO/BMD That would produce widespread ionospheric disturbances that could interrupt radar or infrared sensors for times longer than the attack. ################################# The US has no relevant data on nuclear phenomenology at relevant intercept altitudes. ####################################################### While x-band radars are less susceptible to nuclear blackout, the Achilles heel of Sentinel and Safeguard was random refraction from multiple bursts, for which there is no experimental evidence. ##################### Wopros s 35 ghz i 94 ghz RLS ,budut oni lutsche w dannoj situazii ? s ychetom wozmoznix plusow - ochen' yzkij luch ,dlja cassegran antenni 13.7 metra diametorom 0.014 grad dlja 94 ghz i 0.042 grad dlja 35 ghz i minusow - pri nizkix yglax bolschoe zatuxanie ot atmosferi ,w dozd' rsche xuze Megawatnnie lampi est' na oba diapazona pri depressed traektori wisota poleta mozet bit' 50-60 km pri elevazii 0 grad eto 800 km Y Warlok pri antenne 1.8 metra 94 ghz i impulsnoj moschnosti 100 kwt pri yglax elevazii 30 grad- 700 km pri 0 grad -70 km W 7 raz bolsche antenna = 49 po moschnosti i 10 po moschnsoti = 490.Koren' chetwertoj stepeni daet ywelichenie dalnosti w 4.7 raza Na 35 ghz werojatno lutsche(zatuxanie w atmosfere i ot dozdja mensche ) , no za schet ywelichanija lucha s 0.014 grad w 0.042 grad For attacks greater than a few weapons, this introduces a fundamental uncertainty into ######################################################## NMD. ### Gregory H. Canavan Los Alamos National Laboratory gcanavan@lanl.gov http://www.aps.org/units/fps/newsletters/1999/july/canavan-paper.html
milstar: Возможности современных РЛС с синтезированием апертуры антенны Капитан М. Виноградов, кандидат технических наук Современные радиолокационные средства, устанавливаемые на самолетах и космических аппаратах, в настоящее время представляют один из наиболее интенсивно развивающихся сегментов радиоэлектронной техники. Идентичность физических принципов, лежащих в основе построения этих средств, делает возможным рассмотрение их в рамках одной статьи. Основные различия между космическими и авиационными РЛС заключаются в принципах обработки радиолокационного сигнала, связанными с различным размером апертуры, особенностями распространения радиолокационных сигналов в различных слоях атмосферы, необходимостью учета кривизны земной поверхности и т. д. Несмотря на подобного рода различия, разработчики РЛС с синтезированием апертуры (РСА) прилагают все усилия для того, чтобы добиться максимальной схожести возможностей данных средств разведки. В настоящее время бортовые РЛС с синтезированием апертуры позволяют решать задачи видовой разведки (вести съемку земной поверхности в различных режимах), селекции мобильных и стационарных целей, анализа изменений наземной обстановки, осуществлять съемку объектов, скрытых в лесных массивах, обнаружение заглубленных и малоразмерных морских объектов. Основным назначением РСА является детальная съемка земной поверхности. http://www.pentagonus.ru/publ/89-1-0-1053 За счет искусственного увеличения апертуры бортовой антенны, основной принцип которого заключается в когерентном накоплении отраженных радиолокационных сигналов на интервале синтезирования, удается получить высокое разрешение по углу. В современных системах разрешение может достигать десятков сантиметров при работе в сантиметровом диапазоне длин волн. Аналогичные значения разрешения по дальности достигаются за счет применения внутриимпульсной модуляции, например, линейно-частотной модуляции (ЛЧМ). Интервал синтезирования апертуры антенны прямо пропорционален высоте полета носителя РСА, что обеспечивает независимость разрешения съемки от высоты. В настоящее время существуют три основных режима съемки земной поверхности: обзорный, сканирующий и детальный (рис. 1). В обзорном режиме съемка земной поверхности осуществляется непрерывно в полосе захвата, при этом разделяют боковой и переднебоковой режим (в зависимости от ориентации главного лепестка диаграммы направленности антенны). Накопление сигнала осуществляется в течение времени, равного расчетному интервалу синтезирования апертуры антенны для данных условий полета носителя РЛС. Сканирующий режим съемки отличается от обзорного тем, что съемка ведется на всей ширине полосы обзора, полосами равными ширине полосы захвата. Данный режим используется исключительно в РЛС космического базирования. При съемке в детальном режиме накопление сигнала осуществляется на увеличенном по сравнению с обзорным режимом интервале. Увеличение интервала осуществляется за счет синхронного с движением носителя РЛС перемещения главного лепестка диаграммы направленности антенны таким образом, чтобы облучаемый участок постоянно находился в зоне съемки. Современные системы позволяют получать снимки земной поверхности и расположенных на ней объектов с разрешениями порядка 1 м для обзорного и 0,3 м для детального режимов. Компания «Сандия» анонсировала создание РСА для тактических БЛА, имеющего возможность вести съемку с разрешением 0,1 м в детальном режиме. Существенное значение на результирующие характеристики РСА (в плане съемки земной поверхности) оказывают применяемые методы цифровой обработки принятого сигнала, важной составляющей которых являются адаптивные алгоритмы коррекции траекторных искажений. Именно невозможность выдерживать в течение длительного времени прямолинейную траекторию движения носителя не позволяет получать в непрерывном обзорном режиме съемки разрешения сопоставимые с детальным режимом, хотя никаких физических ограничений на разрешение в обзорном режиме не существует. Режим инверсного синтезирования апертуры (ИРСА) позволяет осуществлять синтезирование апертуры антенны не за счет движения носителя, а за счет движения облучаемой цели. При этом речь может идти не о поступательном движении, характерном для наземных объектов, а о маятниковом движении (в разных плоскостях), характерном для плавучих средств, раскачивающихся на волнах. Данная возможность определяет основное назначение ИРСА - обнаружение и идентификация морских объектов. Характеристики современных ИРСА позволяют уверенно обнаруживать даже малоразмерные объекты, такие как перископы подводных лодок. Вести съемку в данном режиме имеют возможность все самолеты, состоящие на вооружении ВС США и других государств, в задачи которых входит патрулирование береговой зоны и акваторий. Получаемые в результате съемки изображения по своим характеристикам аналогичны изображениям, получаемым в результате съемки с прямым (неинверсным) синтезированием апертуры. Режим интерферометрической съемки (Interferometric SAR - IFSAR) позволяет получать трехмерные изображения земной поверхности. При этом современные системы имеют возможность вести одноточечную съемку (то есть использовать одну антенну) для получения трехмерных изображений. Для характеристики данных изображений помимо обычного разрешения вводится дополнительный параметр, называемый точность определения высоты, или разрешение по высоте. В зависимости от значения данного параметра определяют несколько стандартных градаций трехмерных изображений (DTED - Digital Terrain Elevation Data): dalle na linke http://www.pentagonus.ru/publ/89-1-0-1053 Зарубежное военное обозрение №2 2009 С.52-56
milstar: defense-aerospace.com, 16 февраля 2008 г. Корпорация Northrop Grumman успешно продемонстрировала возможности радара с синтезированной апертурой с высокой разрешающей способностью, созданного на базе РЛС с АФАР истребителя F-22 Raptor ВВС США. «Летные испытания проводились на платформе ВАС 1-11 и теперь можем сказать, что возможности истребителя F-22 существенно расширились, чтобы включать идентификацию и уничтожение наземных мобильных целей, - сказал Тери Маркони (Teri Marconi), вице-президент Combat Avionics Systems at Northrop Grumman. – Это чрезвычайно важное событие для программы F-22, т.к. оно гарантирует «Раптору» детальную информацию и уничтожение врага до того, как он будет обнаружен радаром противника». Испытательные полеты являются первой стадией запланированного многолетнего контракта с компанией Boeing по расширению боевых возможностей существующих и новых серийных вариантов F-22 за счет внедрения режима картографирования земной поверхности с помощью синтезированной апертуры. Сектор электронных систем Northrop Grumman ведет совместную работу с компанией Raytheon по разработке и производству радиолокационной станции истребителя F-22. Northrop Grumman ответственна за полную конструкцию радаров AN/APG-77 и AN/APG-77 (V) 1, последний из которых включает режим работы по наземным целям (синтезированную апертуру). Компания также ответственна за управление и программное обеспечение обработки сигналов и интеграцию радиолокационной системы и испытания. Компания Boeing совместно с основными подрядчиками Lockheed Martin и Pratt & Whitney выполняет интеграцию радара с другими системами бортового радиоэлектронного оборудования F-22, внедрение различных интегрированных программ. http://www.defense-aerospace.com/cgi-bin/client/modele.pl?session=dae.33816982.1203139036.ouGM438AAAEAAComtQIAAAAC&modele=jdc_34
milstar: http://www.ausairpower.net/NCW-101-7.pdf Deployed Systems Multimode radars on fighters and bombers will Since its humble beginnings in the Goodyear be optimised primarily for localised spot APS-73 of 1960, SAR has become almost mapping to support strike operations, with the ubiquitous in modern warfighting, and has exception of the F-22A’s APG-77, which is played a critical role in conflicts since 1991. intended to be used in a primary ISR role. Good The broadest division which exists between examples of this class of radar include variants such radars is that of multimode and attack of the Raytheon APG-73/79 (F/A-18), NG APG- radars with SAR capability, designed primarily to 68(F-16), NG APG-80(F-16), NG APQ-164 (B-1B), support strike operations, and dedicated ISR Raytheon APG-70 (F-15), Raytheon APG-63 (F- radars intended to gather intelligence. 15), NIIP N-001V (Su-27/30) and NIIP N-011M While resolution performance in some of the (Su-30/35), and a number of Phazotron radars. more recent multimode radars carried by What the future will bring will be more fighters or bombers approaches that seen in processing capability, higher resolution, and in dedicated ISR systems, they usually have time advanced features like interferometric limitations in processing capacity, data storage capability. What is clear is that SAR technology capacity, and they typically operate at 8-10 GHz will continue to play a key role in networked which is less than ideal for detecting ground systems. targets. A specialised ISR radar will be designed to gather more data, often from greater ranges, and may often operate in the upper X or Ku- Bands to improve target detection performance. Examples of specialised ISR radars include the massive APY-3 on the E-8C JSTARS, housed in a 26-foot canoe-shaped radome under the fuselage, the ASARS-2 (Advanced Synthetic Aperture Radar System) carried by the U-2, the active array MP-RTIP (Multi-Platform Radar Technology Insertion Program) planned for use on the E-8, E-10 MC2A and RQ-4B Global Hawk UAV, the UK ASTOR system and the APY-8 Lynx on the Predator UAV. While the existing Global Hawk SAR and Predator Lynx have limited power and standoff range, the opposite is true of the APY-3 and its MP-RTIP replacement, both of which will have large effective footprints. The view propounded by some parties in Australia that a fighter radar with SAR capability can provide ‘JSTARS-like’ capability is alas nonsense, since the sheer scale of the radars cannot be compared.
milstar: http://www.aiaa.org/aerospace/images/articleimages/pdf/Index_DEC20082.pdf SAR for UAVs: The next big thing JSTARS will remain the world’s most important manned SAR program for the next 10 years. David L. Rockwell drockwell@tealgroup.com 25 AEROSPACE AMERICA/FEBRUARY 2008 the enlarged USAF RQ-4B Global Hawk, tions about the new APS-137 being devel- Lynx and Lynx II for Predator B, Warrior oped for the MMA). We suspect the Navy ER/MP and Fire Scout, and the Telephon- may buy a full 16 radars for its BMUP ics RDR 1700 maritime radar for Coast Orions, making the APS-149, suddenly, Guard Bell Eagle Eye UAVs. Programs in quite a major program. development include the Navy’s Broad We must congratulate the Navy on its Area Maritime Surveillance UAV (possibly efficient (if secret) procurement. The Navy with an ISAR). is not known for actually getting new sys- MP-RTIP development for Global tems in the field (A-12, P-7, ASPJ, DD(X), Hawk continues unabated, despite can- ATIRCM, J-UCAS, and so on), and they cellations of manned platforms. Fifteen seem to have done an end run to provide a USAF Block 40 Global Hawks with MP- very Air Force-JSTARS-like capability. Six- RTIP are currently planned, with the first teen SAR/GMTI P-3Cs will provide a huge production MP-RTIP radar around 2010 all-weather ISR (intelligence, surveillance, and fielding planned from FY11 to FY15 and reconnaissance) capability. (which we expect will slide right a couple The future: UAVs of years). NATO also plans to buy at least a few Global Hawks with MP-RTIP, with the first systems likely delivered by the middle of the next decade. The first generation Predators B and A, along with their of manned systems resulted in major pro- cousins, the Army’s Warrior ER/MP and grams such as JSTARS. But the few first- I-Gnat, are now receiving a next-genera- generation UAV SARs in service today, on tion replacement for the earlier Northrop Grumman TESAR—General Atomics’ the first generation of endurance UAVs, Lynx and Lynx II. Lynx is probably the are legacy programs from before the UAV best of the new generation of small SARs, spending explosion. Primary among these and though unit cost is well below MP- are Raytheon’s Global Hawk HISAR and RTIP, General Atomics will gain funding Northrop Grumman’s Predator TESAR through sheer numbers produced. The (Tactical Endurance SAR). HISAR will Army has also chosen Lynx II for its Fu- continue in production in upgraded ture Combat System (FCS) Class IV Fire form, while TESAR has already been re- Scout UAV, and the U.K. and the Dept. of moved from service and is being replaced Homeland Security are customers. In by the General Atomics Lynx SAR on the June 2007, the Iraqi air force contracted Predator B. From this very low level, the to buy as many as two dozen Lynx IIs for next generation of UAV SARs will see Beechcraft King Air 350ER ISR aircraft. huge funding growth. Now, with multiple U.S. orders, UAV SAR development funding has General Atomics is also earning RDT&E already risen drastically in the past few funding for technology development, in- years. Initially, most of the increase was cluding the Dual Beam Lynx program, to due to the large MP-RTIP radar for future enhance the capabilities of Lynx to track Global Hawks. But today many smaller slow-moving vehicles more accurately. SAR development programs, including The program modifies a Lynx I radar to upgraded non-MP-RTIP radars for Global create two beams with different phase Hawk, are funding a broader and more centers. It also uses space time adaptive robust increase. Programs entering pro- processing to detect moving targets in the duction soon include a larger HISAR for http://www.aiaa.org/aerospace/images/articleimages/pdf/Index_DEC20082.pdf
milstar: The Lynx SAR operates in the Ku-Band anywhere within the range 15.2 GHz to 18.2 GHz, with 320 W of transmitter power. It is designed to operate and maintain performance specifications in adverse weather, using a Sandia derived weather model that includes 4 mm/hr rainfall. It forms fine- resolution images in real-time and outputs both NTSC video as well as digital images. The Lynx SAR has four primary operating modes. These are described as follows. Lynx is a high resolution, synthetic aperture radar (SAR) that has been designed and built by Sandia National Laboratories in collaboration with General Atomics (GA). Although Lynx may be operated on a wide variety of manned and unmanned platforms, it is primarily intended to be fielded on unmanned aerial vehicles. In particular, it may be operated on the Predator, I-GNAT, or Prowler II platforms manufactured by GA Aeronautical Systems, Inc. The Lynx production weight is less than 120 lb. and has a slant range of 30 km (in 4 mm/hr rain). It has operator selectable resolution and is capable of 0.1 m resolution in spotlight mode and 0.3 m resolution in stripmap mode. In ground moving target indicator mode, the minimum detectable velocity is 6 knots with a minimum target cross-section of 10 dBsm. In coherent change detection mode, Lynx makes registered, complex image comparisons either of 0.1 m resolution (minimum) spotlight images or of 0.3 m resolution (minimum) strip images. The Lynx user interface features a view manager that allows it to pan and zoom like a video camera. Lynx was developed under corporate funding from GA and will be manufactured by GA for both military and commercial applications. The Lynx system architecture will be presented and some of its unique features will be described. Imagery at the finest resolutions in both spotlight and strip modes have been obtained and will also be presented. Keywords: Synthetic Aperture Radar, SAR, Remote Sensing, UAV, MTI, GMTI, CCD 1. INTRODUCTION Lynx is a state of the art, high resolution synthetic aperture radar (SAR). Lynx was designed and built by Sandia National Laboratories and incorporates General Atomics’ design requirements to address a wide variety of manned and unmanned missions. It may be operated on the Predator, I-GNAT, or Prowler II platforms which are manufactured by General Atomics (GA). It may also be operated on manned platforms. Lynx was developed entirely on GA corporate funds. GA is presently beginning the manufacture of Lynx and intends to sell Lynx units and Lynx services to military and commercial customers http://www.sandia.gov/RADAR/lynx.html
milstar: FOR IMMEDIATE RELEASE Oct 21, 2009 GA-ASI's Lynx SAR & Highlighter Sensors Honored Among C4ISR Journal's "Big 25" Technologies SAN DIEGO – 21 October 2009 – General Atomics Aeronautical Systems, Inc. (GA‑ASI), a leading manufacturer of unmanned aircraft systems (UAS), tactical reconnaissance radars, and surveillance systems, today announced the receipt of two awards from C4ISR Journal, the publication of record for the global network-centric warfare community, for GA-ASI’s Lynx® Block 30 Synthetic Aperture Radar (SAR)/Ground Moving Target Indicator (GMTI) sensor system and Highlighter manned aerial electro-optical sensor. In an awards ceremony held October 19 in Arlington, Va., GA-ASI was twice recognized as a finalist in C4ISR Journal’s “Big 25” Awards, a defense industry awards program that honors C4ISR (Command, Control, Communications, Computers, Intelligence, Surveillance, and Reconnaissance) programs, technologies, and organizations that are making a difference on the battlefield or in the defense of civilians against terrorists and insurgents. The company was nominated in the “Sensors” category, which includes devices that gather data that is turned into intelligence, for making a significant difference in the battle zone by deterring enemies and/or gathering intelligence. GA-ASI’s Lynx Block 30 SAR/GMTI radar, a reduced weight/volume version of the Lynx Block 20 system, was recognized for providing the Iraqi Air Force and U.S. Army with the all-weather, wide-area precision search capability to detect time-sensitive targets from both manned and unmanned aircraft platforms. In addition, the company’s Highlighter electro-optical sensor was acknowledged for providing change detection and high-resolution imagery to U.S. Forces deployed in support of counter insurgency and counter-improvised explosive device (IED) efforts. High-resolution photos of the Lynx Block 30 SAR/GMTI are available upon request from the GA-ASI media contact listed below. About GA-ASI General Atomics Aeronautical Systems, Inc., an affiliate of General Atomics, delivers situational awareness by providing unmanned aircraft, radar, and electro-optic solutions for military and commercial applications worldwide. The company’s Aircraft Systems Group is a leading designer and manufacturer of proven, reliable unmanned aircraft systems, including Predator® A, Predator B, Sky Warrior®, and the new Predator C Avenger®. It also manufactures a variety of solid-state digital ground control stations (GCSs), including the next-generation Advanced Cockpit GCS, and provides pilot training and support services for UAS field operations. The Reconnaissance Systems Group designs, manufactures, and integrates the Lynx SAR/GMTI radar and sophisticated CLAW® sensor control and image analysis software into both manned and unmanned aircraft. It also integrates other sensor and communication equipment into manned ISR aircraft and develops emerging technologies in solid-state lasers, electro-optic sensors, and ultra-wideband data links for government applications. For more information, please visit www.ga-asi.com. Lynx, Predator, Sky Warrior, Avenger, and CLAW are registered trademarks of General Atomics Aeronautical Systems, Inc. For more information contact: Kimberly Kasitz Public Relations Manager General Atomics Aeronautical Systems, Inc. +1.858.312.2294 kimberly.kasitz@ga-asi.com http://www.ga-asi.com/news_events/index.php?read=1&id=274
milstar: The front-end microwave components include a TWTA capable of outputting 320 W at 35% duty factor averaged over the Lynx frequency band, and an LNA that allows an overall system noise figure of about 4.5 dB. http://www.sandia.gov/RADAR/lynx.html .pdf file
milstar: LACROSSE-5 Lacrosse-5 launched on the last Titan-4B launched from CCAFS, cost $411 million plus (Ref. SpaceflightNow.com April 7, 2005 launched 04-29-05) indicating that the cost of Lacrosse-5 is perhaps $1,000,000,000.00 - $1,051,000,000.00 billion total including $361 million dollars for the Titan-4B launch for a total cost of $1,411,000.000.00 billion dollars or $411 million for the launch plus $1,000,000,000.00 - $1,051,000,000.00 billion for the satellite equals $1,411,000,000.00 - $1,462,000,000.00 total cost. LACROSSE-6 Lockheed Martin is believed to be building the sixth Lacrosse radar imaging spacecraft in the series to bridge the gap between it and the Future Imagery Architecture radar spacecraft of Boeing believed to be more advanced in development possible nearing completion and flight testing. This and several other kinds of existing spacecraft are being built to bridge the FIA gap if scheduling development issues arise as they already have occurred. The FIA photo imagining systems have already had the photo imaging spacecraft prime contractor changed from Boeing to Lockheed Martin creating considerable delay in that program. http://www.globalsecurity.org/space/systems/lacrosse.htm http://www.globalsecurity.org/space/systems/images/lacrosse1.jpg
milstar: LACROSSE / ONYX Despite its many advances, the KH-12 suffers the shortcoming common to all photographic intelligence satellites, the inability to see through clouds. With much of the (former) Soviet Union and other areas of interest frequently covered with clouds, this has always posed a problem for intelligence collection. However, in the past, this problem was primarily one of directing the satellite's coverage toward cloud-free areas, and awaiting improved visibility in cloudy regions. While this procedure may have been adequate for peace-time operations, it is clearly inadequate for war-time target acquisition. A typical radar (RAdio Detection and Ranging) measures the strength and round-trip time of the microwave signals that are emitted by a radar antenna and reflected off a distant surface or object. The radar antenna alternately transmits and receives pulses at particular microwave wavelengths (in the range 1 cm to 1 m, which corresponds to a frequency range of about 300 MHz to 30 GHz) and polarizations (waves polarized in a single vertical or horizontal plane). For an imaging radar system, about 1500 high-power pulses per second are transmitted toward the target or imaging area, with each pulse having a pulse duration (pulse width) of typically 10-50 microseconds (us). The pulse normally covers a small band of frequencies, centered on the frequency selected for the radar. At the Earth's surface, the energy in the radar pulse is scattered in all directions, with some reflected back toward the antenna. This backscatter returns to the radar as a weaker radar echo and is received by the antenna in a specific polarization (horizontal or vertical, not necessarily the same as the transmitted pulse). Given that the radar pulse travels at the speed of light, it is relatively straightforward to use the measured time for the roundtrip of a particular pulse to calculate the distance or range to the reflecting object. The chosen pulse bandwidth determines the resolution in the range (cross-track) direction. Higher bandwidth means finer resolution in this dimension. The length of the radar antenna determines the resolution in the azimuth (along-track) direction of the image: the longer the antenna, the finer the resolution in this dimension. Synthetic Aperture Radar (SAR) refers to a technique used to synthesize a very long antenna by combining signals (echoes) received by the radar as it moves along its flight track. Aperture means the opening used to collect the reflected energy that is used to form an image. In the case of a camera, this would be the shutter opening; for radar it is the antenna. A synthetic aperture is constructed by moving a real aperture or antenna through a series of positions along the flight track. As the radar moves, a pulse is transmitted at each position; the return echoes pass through the receiver and are recorded in an 'echo store.' Because the radar is moving relative to the ground, the returned echoes are Doppler-shifted (negatively as the radar approaches a target; positively as it moves away). Comparing the Doppler-shifted frequencies to a reference frequency allows many returned signals to be "focused" on a single point, effectively increasing the length of the antenna that is imaging that particular point. This focusing operation, commonly known as SAR processing, is now done digitally on fast computer systems. The trick in SAR processing is to correctly match the variation in Doppler frequency for each point in the image: this requires very precise knowledge of the relative motion between the platform and the imaged objects (which is the cause of the Doppler variation in the first place). Synthetic aperture radar is now a mature technique used to generate radar images in which fine detail can be resolved. SARs provide unique capabilities as an imaging tool. Because they provide their own illumination (the radar pulses), they can image at any time of day or night, regardless of sun illumination. And because the radar wavelengths are much longer than those of visible or infrared light, SARs can also "see" through cloudy and dusty conditions that visible and infrared instruments cannot. Radar images are composed of many dots, or picture elements. Each pixel (picture element) in the radar image represents the radar backscatter for that area on the ground: darker areas in the image represent low backscatter, brighter areas represent high backscatter. Bright features mean that a large fraction of the radar energy was reflected back to the radar, while dark features imply that very little energy was reflected. Backscatter for a target area at a particular wavelength will vary for a variety of conditions: size of the scatterers in the target area, moisture content of the target area, polarization of the pulses, and observation angles. Backscatter will also differ when different wavelengths are used. Backscatter is also sensitive to the target's electrical properties, including water content. Wetter objects will appear bright, and drier targets will appear dark. The exception to this is a smooth body of water, which will act as a flat surface and reflect incoming pulses away from a target; these bodies will appear dark. Backscatter will also vary depending on the use of different polarization. Some SARs can transmit pulses in either horizontal (H) or vertical (V) polarization and receive in either H or V, with the resultant combinations of HH (Horizontal transmit, Horizontal receive), VV, HV, or VH. Additionally, some SARs can measure the phase of the incoming pulse (one wavelength = 2pi in phase) and therefore measure the phase difference (in degrees) in the return of the HH and VV signals. Track angle will affect backscatter from very linear features: urban areas, fences, rows of crops, ocean waves, fault lines. The angle of the radar wave at the Earth's surface (called the incidence angle) will also cause a variation in the backscatter: low incidence angles (perpendicular to the surface) will result in high backscatter; backscatter will decrease with increasing incidence angles. A space-based imaging radar can see through clouds, and utilization of synthetic aperture radar (SAR) techniques can potentially provide images with a resolution that approaches that of photographic reconnaissance satellites. A project to develop such a satellite was initiated in late 1976 by then-Director of Central Intelligence George Bush. This effort led to the successful test of the Indigo prototype imaging radar satellite in January 1982. Although the decision to proceed with an operational system was very controversial, development of the Lacrosse system was approved in 1983. The distinguishing features of the design of the Lacrosse satellite include a very large radar antenna, and solar panels to provide electrical power for the radar transmitter. Reportedly, the solar arrays have a wingspan of almost 50 meters, which suggests that the power available to the radar could be in the range of 10 to 20 kilowatts, as much as ten times greater than that of any previously flown space-based radar. It is difficult to assess the resolution that could be achieved by this radar in the absence of more detailed design information, but in principle the resolution might be expected to be better than one meter. While this is far short of the 10 centimeter resolution achievable with photographic means, it would certainly be adequate for the identification and tracking of major military units such as tanks or missile transporter vehicles. However, this high resolution would come at the expense of broad coverage, and would be achievable over an area of only a few tens of kilometers square. Thus the Lacrosse probably utilizes a variety of radar scanning modes, some providing high resolution images of small areas, and other modes offering lower resolution images of areas several hundred kilometers square. The processing of this data would require extensive computational power, requiring the transmission to ground stations of potentially several hundred mega-bits of data per second. Lacrosse 1 (1988-106B 19671) was launched on 2 December 1988 by the Space Shuttle. The spacecraft entered an orbit with an inclination of 57 degrees, with an perigee of 680 kilometers and an apogee of 690 kilometers, and had not maneuvered significantly since launch. http://www.fas.org/spp/military/program/imint/lacrosse.htm
milstar: What is Imaging Radar ? by Tony Freeman, Jet Propulsion Laboratory An imaging radar works very like a flash camera in that it provides its own light to illuminate an area on the ground and take a snapshot picture, but at radio wavelengths. A flash camera sends out a pulse of light (the flash) and records on film the light that is reflected back at it through the camera lens. Instead of a camera lens and film, a radar uses an antenna and digital computer tapes to record its images. In a radar image, one can see only the light that was reflected back towards the radar antenna. A typical radar (RAdio Detection and Ranging) measures the strength and round-trip time of the microwave signals that are emitted by a radar antenna and reflected off a distant surface or object. The radar antenna alternately transmits and receives pulses at particular microwave wavelengths (in the range 1 cm to 1 m, which corresponds to a frequency range of about 300 MHz to 30 GHz) and polarizations (waves polarized in a single vertical or horizontal plane). For an imaging radar system, about 1500 high- power pulses per second are transmitted toward the target or imaging area, with each pulse having a pulse duration (pulse width) of typically 10-50 microseconds (us). The pulse normally covers a small band of frequencies, centered on the frequency selected for the radar. Typical bandwidths for an imaging radar are in the range 10 to 200 MHz. At the Earth's surface, the energy in the radar pulse is scattered in all directions, with some reflected back toward the antenna. Thisbackscatter returns to the radar as a weaker radar echo and is received by the antenna in a specific polarization (horizontal or vertical, not necessarily the same as the transmitted pulse). These echoes are converted to digital data and passed to a data recorder for later processing and display as an image. Given that the radar pulse travels at the speed of light, it is relatively straightforward to use the measured time for the roundtrip of a particular pulse to calculate the distance or range to the reflecting object. The chosen pulse bandwidth determines the resolution in the range (cross-track) direction. Higher bandwidth means finer resolution in this dimension. Radar transmits a pulse Measures reflected echo (backscatter ) Click Here to See Animation In the case of imaging radar, the radar moves along a flight path and the area illuminated by the radar, or footprint, is moved along the surface in a swath, building the image as it does so. Building up a radar image using the motion of the platform The length of the radar antenna determines the resolution in the azimuth (along-track) direction of the image: the longer the antenna, the finer the resolution in this dimension. Synthetic Aperture Radar (SAR) refers to a technique used to synthesize a very long antenna by combining signals (echoes) received by the radar as it moves along its flight track. Aperture means the opening used to collect the reflected energy that is used to form an image. In the case of a camera, this would be the shutter opening; for radar it is the antenna. A synthetic aperture is constructed by moving a real aperture or antenna through a series of positions along the flight track. Constructing a Synthetic Aperture As the radar moves, a pulse is transmitted at each position; the return echoes pass through the receiver and are recorded in an 'echo store.' Because the radar is moving relative to the ground, the returned echoes are Doppler-shifted (negatively as the radar approaches a target; positively as it moves away). Comparing the Doppler-shifted frequencies to a reference frequency allows many returned signals to be "focused" on a single point, effectively increasing the length of the antenna that is imaging that particular point. This focusing operation, commonly known as SAR processing, is now done digitally on fast computer systems. The trick in SAR processing is to correctly match the variation in Doppler frequency for each point in the image: this requires very precise knowledge of the relative motion between the platform and the imaged objects (which is the cause of the Doppler variation in the first place). Synthetic aperture radar is now a mature technique used to generate radar images in which fine detail can be resolved. SARs provide unique capabilities as an imaging tool. Because they provide their own illumination (the radar pulses), they can image at any time of day or night, regardless of sun illumination. And because the radar wavelengths are much longer than those of visible or infrared light, SARs can also "see" through cloudy and dusty conditions that visible and infrared instruments cannot. What is a radar image? Radar images are composed of many dots, or picture elements. Each pixel (picture element) in the radar image represents the radar backscatter for that area on the ground: darker areas in the image represent low backscatter, brighter areas represent high backscatter. Bright features mean that a large fraction of the radar energy was reflected back to the radar, while dark features imply that very little energy was reflected. Backscatter for a target area at a particular wavelength will vary for a variety of conditions: size of the scatterers in the target area, moisture content of the target area, polarization of the pulses, and observation angles. Backscatter will also differ when different wavelengths are used. Scientists measure backscatter, also known as radar cross section, in units of area (such as square meters). The backscatter is often related to the size of an object, with objects approximately the size of the wavelength (or larger) appearing bright (i.e. rough) and objects smaller than the wavelength appearing dark (i.e. smooth). Radar scientists typically use a measure of backscatter called normalized radar cross section, which is independent of the image resolution or pixel size. Normalized radar cross section (sigma0.) is measured in decibels (dB). Typical values of sigma0. for natural surfaces range from +5dB (very bright) to -40dB (very dark). A useful rule-of-thumb in analyzing radar images is that the higher or brighter the backscatter on the image, the rougher the surface being imaged. Flat surfaces that reflect little or no microwave energy back towards the radar will always appear dark in radar images. Vegetation is usually moderately rough on the scale of most radar wavelengths and appears as grey or light grey in a radar image. Surfaces inclined towards the radar will have a stronger backscatter than surfaces which slope away from the radar and will tend to appear brighter in a radar image. Some areas not illuminated by the radar, like the back slope of mountains, are in shadow, and will appear dark. When city streets or buildings are lined up in such a way that the incoming radar pulses are able to bounce off the streets and then bounce again off the buildings (called a double- bounce) and directly back towards the radar they appear very bright (white) in radar images. Roads and freeways are flat surfaces so appear dark. Buildings which do not line up so that the radar pulses are reflected straight back will appear light grey, like very rough surfaces. Imaging different types of surface with radar Backscatter is also sensitive to the target's electrical properties, including water content. Wetter objects will appear bright, and drier targets will appear dark. The exception to this is a smooth body of water, which will act as a flat surface and reflect incoming pulses away from a target; these bodies will appear dark. Backscatter will also vary depending on the use of different polarization. Some SARs can transmit pulses in either horizontal (H) or vertical (V) polarization and receive in either H or V, with the resultant combinations of HH (Horizontal transmit, Horizontal receive), VV, HV, or VH. Additionally, some SARs can measure the phase of the incoming pulse (one wavelength = 2pi in phase) and therefore measure the phase difference (in degrees) in the return of the HH and VV signals. This difference can be thought of as a difference in the roundtrip times of HH and VV signals and is frequently the result of structural characteristics of the scatterers. These SARs can also measure the correlation coefficient for the HH and VV returns, which can be considered as a measure of how alike (between 0/not alike and 1/alike) the HH and VV scatterers are. Different observations angles also affect backscatter. Track angle will affect backscatter from very linear features: urban areas, fences, rows of crops, ocean waves, fault lines. The angle of the radar wave at the Earth's surface (called the incidence angle) will also cause a variation in the backscatter: low incidence angles (perpendicular to the surface) will result in high backscatter; backscatter will decrease with increasing incidence angles. Radar backscatter is a function of incidence angle, (theta)i NASA/JPL's Radar Program NASA/JPL's radar program began with the SEASAT synthetic aperture radar (SAR) in 1978. SEASAT was a single frequency (L-band with lambda ~ 24 cm or 9.4 inches), single polarization, fixed-look angle radar. The Shuttle Imaging Radar-A (SIR-A), flown on the Space Shuttle in 1981, was also an L- band radar with a fixed look angle. SIR-B (1984) added a multi-look angle capability to the L-band, single polarization radar. SIR-C/X-SAR is a joint venture of NASA, the German Space Agency (DARA), and the Italian Space Agency (ASI). SIR-C/X-SAR provided increased capability over Seasat, SIR-A, and SIR-B by acquiring images at three microwave wavelengths (lambda), L- band (lambda ~ 24 cm or 9.4 inches) quad-polarization; C-band (lambda ~ 6 cm or 2.4 inches) quad- polarization; and X-band (lambda ~ 3 cm) with VV polarization. SIR-C/X-SAR also has a variable look angle, and can image at incidence angles between 20 and 65 degrees. SIR-C/X-SAR flew on the shuttle in April and in October of 1994, providing radar data for two seasons. Typical image sizes for SIR-C data products are 50kmx100km, with resolution between10 and 25 meters in both dimensions. Parallel to the development of spaceborne imaging radars, NASA/JPL have built and operated a series of airborne imaging radar systems. NASA/JPL currently maintain and operate an airborne SAR system, known as AIRSAR/TOPSAR, which flies on a NASA DC-8 jet. In one mode of operation, this system is capable of simultaneously collecting all four polarizations (HH,HV, VH and VV) for three frequencies: L- band (lambda ~ 24 cm); C-band (lambda ~ 6 cm) ; and P-band (lambda ~ 68 cm). In another mode of operation, the AIRSAR/TOPSAR system collects all four polarizations (HH,HV, VH and VV) for two frequencies: L- band (lambda ~ 24 cm); and P-band (lambda ~ 68 cm), while operating as an interferometer at C-band to simultaneously generate topographic height data. AIRSAR/TOPSAR also has an along-track interferometer mode which is used to measure current speeds. Typical image sizes for AIRSAR/TOPSAR products are 12kmx12km, with 10 meter resolution in both dimensions. Topographic map products generated by the TOPSAR system have been shown to have a height accuracy of1 m in relatively flat areas, and 5 m height accuracy in mountainous areas. JPL are studying designs for a free-flying multi- parameter imaging radar system like the one flown during the SIR-C/X-SAR missions. JPL are also studying a global mapping mission (TOPSAT) which will use radar interferometry to generate high quality topographic maps over the whole world and monitor changes in topography in areas prone to earthquakes and volcanic activity. To inquire about the availability of imaging radar data from the SIR-C, SIR-B, SIR-A or Seasat missions, or the airborne AIRSAR/TOPSAR system, please contact: Radar Data Center Mail Stop 300 - 233 Jet Propulsion Laboratory 4800 Oak Grove Drive http://southport.jpl.nasa.gov/desc/imagingradarv3.html Pasadena, CA 91109 Fax: (818) 393 2640 Other Contact Information To learn more about NASA/JPL's Imaging Radar Program, if you are an Internet user, please refer to World Wide Web server site at URL: http://southport.jpl.nasa.gov/
milstar: http://en.wikipedia.org/wiki/File:Lacrosse_const_aug09.png
milstar: http://www.raytheon.com/businesses/stellent/groups/sas/documents/asset/apy10_ds.pdf Periscope Detection Mode Optimized for detection of small targets with limited exposure time in high sea states PPI display range to 32 nmi, with B-scan “zoom” 256 target TWS Surface Search Mode Optimized for long-range detection of maritime targets PPI display range to 200 nmi, with B-scan “zoom” 256 target TWS
milstar: For example, the United Kingdom's ASTOR (Airborne Stand-Off Radar) program, which is expected to have initial operational capability in 2007 and full fleet in operation in 2008, is an airborne, ground-surveillance radar which employs a passive phased array design. ##################################################### The use of T/R modules in active arrays provides the advantages of amplitude control, low loss, and graceful degradation over passive arrays. Given these advantages, one could assume that all phased arrays in development are active. In fact, despite the large investment that the U.S. Government has made in the development of T/R modules beginning in 1964, the high cost and low efficiency of the modules has proven to be an obstacle to development of active phased array antennas Raytheon chose to use phase shifters, rather than T/R modules, citing concern over size, ######################################################## weight, power and technical risks. ###################### http://www.emsdss.com/uploadedFiles/pdf/PassivePhasedArrays.pdf A final example is the Joint Surveillance Target Attack Radar System (JSTARS), an airborne phased array used in a synthetic aperture radar. It is a long-range, air-to-ground surveillance system designed to locate, classify and track ground targets in all weather conditions, and it provides the combatant commanders with the best situational awareness data available
milstar: Космический радиолокатор с синтезированной апертурой обзора земной поверхности Современный этап развития космических РЛ-средств дистанционного зондирования Земли характеризуется созданием РЛС с синтезированной апертурой 3-го поколения, а также существенным прогрессом в использовании информации для решения практических задач. “Концерн “Вега” имеет уникальный и успешный практический опыт создания космической аппаратуры РЛ-наблюдения. Это бортовые комплексы “Чайка” КА серии “Космос” с РЛС бокового обзора для наблюдения морской поверхности и автоматического обнаружения кораблей (36 пусков в течении 19 лет), РЛС с синтезированной апертурой “Меч-К” и “Меч-КУ” для дистанционного зондирования Земли с КА “Космос-1870” (1987-1989 гг.) и “Алмаз-1”(1991-1992 гг.) Ближайшая перспектива существенно повысить информативность космических средств радиолокационного зондирования Земли на мировом уровне должна осуществиться при вводе в эксплуатацию радиолокатора с синтезированной апертурой антенны, спроектированного ОАО «Концерном радиостроения «Вега» в качестве полезной нагрузки для космического аппарата "Кондор-Э", разрабатываемого ОАО «ВПК «НПО машиностроения». К настоящему времени изготовлен, прошёл наземную отработку и передан в ОАО «ВПК «НПО машиностроения» для установки на КА «Кондор-Э» лётный комплект РСА. http://www.vega.su/catalog/index44.php
milstar: СССР стоял у истоков создания радиолокационных систем зондирования Земли - первый советский спутник с радаром S-диапазона с синтезированной апертурой "Алмаз Т1", разрешение снимков которого ориентировочно должно было составить 10 - 15 метров, был готов к старту уже в 1981 году, хотя непосредственно перед стартом программа была законсервирована до 1986 года. http://news.cosmoport.com/2005/11/10/8.htm “Концерн “Вега” имеет уникальный и успешный практический опыт создания космической аппаратуры РЛ-наблюдения. Это бортовые комплексы “Чайка” КА серии “Космос” с РЛС бокового обзора для наблюдения морской поверхности и автоматического обнаружения кораблей (36 пусков в течении 19 лет), РЛС с синтезированной апертурой “Меч-К” и “Меч-КУ” для дистанционного зондирования Земли с КА “Космос-1870” (1987-1989 гг.) и “Алмаз-1”(1991-1992 гг.) http://www.vega.su/catalog/index44.php Сегодня у России собственных радиолокационных спутников зондирования Земли не имеется, как, впрочем, и более привычных спутников, работающих в оптическом и инфракрасном диапазонах. Тем временем другие страны ведут активные работы по созданию собственных спутниковых радаров для наблюдения Земли. ФРГ готовится развернуть сеть SAR-Lupe, предназначенную для Бундесвера. В 2006 году канадская компания-оператор MDA's Geospatial Services International планирует вывести на орбиту второй спутник RADARSAT-2 с более совершенным радиолокатором, позволяющим получать изображения с разрешением до 3м. http://news.cosmoport.com/2005/11/10/8.htm
milstar: Преимущества http://www.vega.su/catalog/index44.php Уникальное преимущество РСА малого КА “Кондор-Э” – выбор дециметрового S-диапазона, сочетающего высокую разрешающую способность (около 1 м) для распознавания и измерения параметров объектов наблюдения с лучшими, в сравнении с см-диапазонами X и C изобразительными возможностями. Opticheskaja razwedka s diametrom cassegr antenni 2.2-2.6 metra primerno 10 sm(Keyhole ,Hubble ) ,s adaptiwnoj optikoj do 1-2 sm (chitat' nomer amaschini iz kosmosa) w lutschix yslowijax Ключевыми решениями, принятыми при выборе облика РСА были: * выбор рабочей длины волны в S диапазоне (9,5 см); * применение зеркальной антенны с рефлектором диаметром 6 м, разработки ОКБ МЭИ; Такая антенна имеет большую эффективную площадь, необходимую для расширения полосы обзора до 500 км с механическим разворотом для двустороннего обзора, легче и дешевле, чем АФАР; * применениее цифрового формирователя сигналов и частот с гибким управлением, позволяющим в широких пределах менять параметры импульсов в рабочих и калибровочных режимах и для проведения экспериментов; * использование транзисторного выходного усилителя с суммированием мощности 16 модулей, обеспечивающего более 200 Вт средней мощности излучения с запасом на проведение экспериментов; * использование в приемнике оригинального циклотронного защитного устройства, быстродействующих ограничителей и цифровых аттенюаторов, управляемых по программе или от цифрового АРУ; * предусмотрены режимы работы с ГГ или ВВ поляризациями. Прием перекрестных поляризаций не предусмотрен, но ожидается, что высокое разрешение облегчит идентификацию подстилающей поверхности по текстурным признакам. Rassmotret' wozmoznost' powischenija razr. sposobnosti SAR kosmicheskogo bazirowanija
milstar: A space-based imaging radar can see through clouds, and utilization of synthetic aperture radar (SAR) techniques can potentially provide images with a resolution that approaches that of photographic reconnaissance satellites. A project to develop such a satellite was initiated in late 1976 by then-Director of Central Intelligence George Bush. ######################################################################### http://www.fas.org/spp/military/program/imint/lacrosse.htm The distinguishing features of the design of the Lacrosse satellite include a very large radar antenna, and solar panels to provide electrical power for the radar transmitter. Reportedly, the solar arrays have a wingspan of almost 50 meters, which suggests that the power available to the radar could be in the range of 10 to 20 kilowatts, as much as ten times greater than that of any previously flown space-based radar. Est' proekti jadernix reaktorow kosmicheskogo bazirowanija FGUP KB Arsenal 7200 kg -100 kwt ! It is difficult to assess the resolution that could be achieved by this radar in the absence of more detailed design information, but in principle the resolution might be expected to be better than one meter. ########################################################### While this is far short of the 10 centimeter resolution achievable with photographic means, it would certainly be adequate for the identification and tracking of major military units such as tanks or missile transporter vehicles. However, this high resolution would come at the expense of broad coverage, and would be achievable over an area of only a few tens of kilometers square. ############################### Thus the Lacrosse probably utilizes a variety of radar scanning modes, some providing high resolution images of small areas, and other modes offering lower resolution images of areas several hundred kilometers square. The processing of this data would require extensive computational power, requiring the transmission to ground stations of potentially several hundred mega-bits of data per second. prinzipialnnie nedostatki -wisoskoe razreschenie -nizkaja orbita . Legko sbiwaetsja ( w tom chisle i sistemami tipa THAAD/S-400 ) .Sputniki ne obladajut manewr. ballisticheskix boegolovok MARV - Bolschoj ob'em peredawaemij dannix .Sistema bolee legko gluschitsja chem Milstar s boewoj nagruzkoj dlja jadernoj wojni ( 75 bit/sec)
milstar: Alternativi SAR kosmicheskogo bazirowanija http://www.cbo.gov/ftpdocs/76xx/doc7691/01-03-SpaceRadar.pdf Costs of the Alternatives Total life-cycle costs for the four illustrative Space Radar systems that CBO examined would range from about $26 billion to $94 billion (in 2007 dollars), ############################# Alternatives 1, 2, and 4 Alternative 3 Active electronically steered array Active electronically steered array 16 x 2.5 m (40 m2) 25 x 4 m (100 m2) 1,000 km 1,000 km 53° 53° 10 GHz (X band) 10 GHz (X band) 1,500 watts 1,500 watts SAR 1 GHz 1 GHz GMTI 15 MHz 15 MHz 15 percent 15 percent SAR 15°–70° 8°–70° GMTI 6°–70° 6°–70° SAR ±45° electronic steering ±45° electronic steering GMTI 360° mechanical steering 360° mechanical steering ±21° electronic steering ±21° electronic steering 5,000 watts 7,000 watts Enough battery capacity to operate radar Enough battery capacity to operate radar for 30 minutes per 105-minute orbit for 30 minutes per 105-minute orbit 10 years 10 years
milstar: The area that can be covered per day varies with the resolution of the imagery. At 0.1-meter resolution, the reference constellation in Alternative 2 could image about 5,500 square kilometers per day in North Korea, CBO estimates (see Figure 4-4).5 To put that area in perspective, CBO compared it with several benchmarks. For example, a single mechanized division in a defensive posture, using former Soviet tactics, could be expected to ###################################### occupy an area of 500 to 1,000 square kilometers.6 Thus, ##################################### Alternative 2’s constellation could image about 5 to 10 ##################################### divisions in a day. As another example, during the 1991 Persian Gulf War, the Air Force divided Iraq into boxes that measured 30 arc minutes on a side for the purpose of detecting and targeting transporter erector launchers (TELs) for Scud missiles.7 A box of those dimensions placed in North Korea would have an area of approximately 2,400 square kilometers. The constellation in ############################## Alternative 2 could image two such boxes per day at 0.1-meter resolution. ############## The same size constellation with larger radars (Alternative 3) could image more than nine such boxes per day. ################ Area coverage increases rapidly as the required resolution becomes coarser. At 0.15-meter resolution, Alternative 2 ###################################### could image slightly more than 20,000 square kilometers ###################################### in one day, ######### equivalent to an area spanning the entire width of the Korean demilitarized zone and extending about 80 kilometers into North Korea. At 1-meter resolution, Alternative 2 could image about 600,000 square kilometers per day, or nearly three times the entire 220,000-square-kilometer land area of the Korean Peninsula (see Figure 4-5). Even the five-satellite constellation in Alternative 1 would be capable of imaging the entire land area of the Korean Peninsula in one day at 0.7-meter resolution.
полная версия страницы