{"id":15592,"date":"2020-04-28T11:41:08","date_gmt":"2020-04-28T15:41:08","guid":{"rendered":"https:\/\/iridian.com.cn\/?page_id=15592"},"modified":"2021-11-08T05:42:39","modified_gmt":"2021-11-08T10:42:39","slug":"applications-earth-observation","status":"publish","type":"page","link":"https:\/\/iridian.com.cn\/en\/applications-earth-observation\/","title":{"rendered":"Earth Observation Optical Filters"},"content":{"rendered":"<p>[et_pb_section fb_built=&#8221;1&#8243; _builder_version=&#8221;4.9.11&#8243; custom_margin=&#8221;0px||||false|false&#8221; custom_padding=&#8221;0px||||false|false&#8221; global_colors_info=&#8221;{}&#8221;][et_pb_row _builder_version=&#8221;4.9.11&#8243; width=&#8221;100%&#8221; custom_margin=&#8221;0px||||false|false&#8221; custom_padding=&#8221;0px||||false|false&#8221; global_colors_info=&#8221;{}&#8221;][et_pb_column type=&#8221;4_4&#8243; _builder_version=&#8221;4.3.4&#8243; global_colors_info=&#8221;{}&#8221;][et_pb_image src=&#8221;https:\/\/iridian.com.cn\/wp-content\/uploads\/2017\/09\/earth2_720.jpg&#8221; align=&#8221;center&#8221; force_fullwidth=&#8221;on&#8221; _builder_version=&#8221;4.4.8&#8243; global_colors_info=&#8221;{}&#8221;][\/et_pb_image][et_pb_text _builder_version=&#8221;4.4.8&#8243; global_colors_info=&#8221;{}&#8221;]<\/p>\n<p>The view from outside often provides unique insights into an environment as it can be extraordinarily difficult to objectively observe a system from within.\u00a0 Once the ability to \u201cslip the surly bonds of earth\u201d was established in the 1960\u2019s it quickly became a race to exploit the ability to observe our earth from above by deploying satellites with capabilities for earth observation (EO). From the first space-based multispectral imager (MSI), Landsat-1, launched by NASA in 1972 to the current proliferation of constellations of commercial cubesats, EO systems rely on the ability to differentiate the optical signal of interest from the noise, often employing wavelength selective optical filters for this purpose.<\/p>\n<p>By their nature optical filters provide wavelength selectivity to the instruments in which they are employed.\u00a0 In EO systems, single selective wavelength bands are often necessary to allow observation of unique spectral characteristics representative of specific phenomena of interest exploiting\u00a0 unique wavelength bands that are reflected, transmitted, or absorbed from different atmospheric and terrestrial constituents with different chemical compositions.<\/p>\n<p>Optical filters provide can provide wavelength selectivity to these systems either as single band-pass filters (BPF) to interrogate one wavelength region of interest or as multi-zone filter (MZF) arrays that can turn a single detector into a multi-spectral device capable of analyzing different wavelengths and the associated phenomena of interest.<\/p>\n<p>[\/et_pb_text][et_pb_text admin_label=&#8221;YouTube&#8221; _builder_version=&#8221;4.5.0&#8243; width=&#8221;65%&#8221; module_alignment=&#8221;center&#8221; global_colors_info=&#8221;{}&#8221;]<\/p>\n<p><iframe loading=\"lazy\" title=\"Optical Filters for Earth Observation\" width=\"1080\" height=\"608\" src=\"https:\/\/www.youtube.com\/embed\/wiqq1jKMQco?feature=oembed\"  allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture\" allowfullscreen><\/iframe><\/p>\n<p>&nbsp;<\/p>\n<p>[\/et_pb_text][et_pb_text admin_label=&#8221;Multi-zone Filter Arrays&#8221; _builder_version=&#8221;4.4.8&#8243; global_colors_info=&#8221;{}&#8221;]<\/p>\n<p><span style=\"color: #3366ff;\"><strong>Multi-zone Filter Arrays<\/strong><\/span> help turn single detectors into multi-spectral imaging devices where different rows of pixels will image and detect different wavelength selective science bands of interest.<\/p>\n<p>MZFs at Iridian can be manufactured by patterning and depositing individual zones on a monolithic substrate, by mechanical assembly of individual bars into a single robust array (\u201cbutcher-block\u201d), or by a hybrid approach combining both assembled zones with patterned features (such as black seam or letterbox coatings) or true hybrids where patterned zones are assembled together into a larger \u201cbutcher-block\u201d array.<\/p>\n<p>Typical MZF array performance requirements include:<\/p>\n<ul>\n<li>narrow passband regions with high transmittance (Tx) within each band<\/li>\n<li>deep and broad out of band and band-to-band blocking\n<ul>\n<li>steep edges to provide a sharp transition from Tx to blocking<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<ul>\n<li>small and controlled zone-to-zone transition widths to maximize usable pixels\n<ul>\n<li>typically &lt;50um for patterned arrays and &lt;200um for \u201cbutcher-block\u201d arrays<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<ul>\n<li>robust to survive in orbit (solar radiation durability)<\/li>\n<li>durable array construction to survive rigors of launch<\/li>\n<\/ul>\n<p>[\/et_pb_text][et_pb_text admin_label=&#8221;Images&#8221; _builder_version=&#8221;4.4.8&#8243; global_colors_info=&#8221;{}&#8221;]<\/p>\n<p><a href=\"https:\/\/iridian.com.cn\/wp-content\/uploads\/2020\/06\/earth01.png\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-15961 alignnone size-full\" src=\"https:\/\/iridian.com.cn\/wp-content\/uploads\/2020\/06\/earth01.png\" alt=\"\" width=\"160\" height=\"119\" \/><\/a> <a href=\"https:\/\/iridian.com.cn\/wp-content\/uploads\/2020\/06\/earth02.png\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-15959 alignnone size-large\" src=\"https:\/\/iridian.com.cn\/wp-content\/uploads\/2020\/06\/earth02.png\" alt=\"\" width=\"140\" height=\"140\" srcset=\"https:\/\/iridian.com.cn\/wp-content\/uploads\/2020\/06\/earth02.png 140w, https:\/\/iridian.com.cn\/wp-content\/uploads\/2020\/06\/earth02-100x100.png 100w\" sizes=\"(max-width: 140px) 100vw, 140px\" \/><\/a> <a href=\"https:\/\/iridian.com.cn\/wp-content\/uploads\/2020\/06\/earth03.png\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-15957 alignnone size-large\" src=\"https:\/\/iridian.com.cn\/wp-content\/uploads\/2020\/06\/earth03.png\" alt=\"\" width=\"160\" height=\"104\" \/><\/a> <a href=\"https:\/\/iridian.com.cn\/wp-content\/uploads\/2020\/06\/earth04.png\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-15955 alignnone size-full\" src=\"https:\/\/iridian.com.cn\/wp-content\/uploads\/2020\/06\/earth04.png\" alt=\"\" width=\"266\" height=\"82\" \/><\/a><\/p>\n<p>[\/et_pb_text][et_pb_text disabled_on=&#8221;on|on|on&#8221; _builder_version=&#8221;4.4.3&#8243; disabled=&#8221;on&#8221; global_colors_info=&#8221;{}&#8221;]<\/p>\n<div class=\"et_pb_module et_pb_text et_pb_text_0 et_pb_text_align_left et_pb_bg_layout_light\">\n<div class=\"et_pb_text_inner\">\n<h1 style=\"text-align: center;\">Eyes in the Skies- Optical Filters for Earth Observation<\/h1>\n<p>&nbsp;<\/p>\n<p style=\"text-align: center;\"><em>\u201cMeasurement is the first step that leads to control and eventually to improvement. If you can\u2019t measure something, you can\u2019t understand it. If you can\u2019t understand it, you can\u2019t control it.\u00a0 If you can\u2019t control it, you can\u2019t improve it.\u201d<\/em><\/p>\n<h5 style=\"text-align: center;\">H. James Harrington<\/h5>\n<p>&nbsp;<\/p>\n<p>Since the agricultural revolutionmore than 10,000 years ago humans have increasingly sought ways to manage and improve our local and global environments. In the modern world we have become increasingly dependent on the ability to control or at the very least understand, for purposes of commerce, safety and security, and science, our environment and our impact\/interaction with it. This includes a desire for increased understanding of natural and man-made or influenced phenomena such as forest fires, lightning, atmospheric constituents (clouds and aerosols), weather (storms), ocean temperatures\/currents, forests and deforestation, crops\/surface cover and albedo, sea-ice, and oil spills.\u00a0 An improved ability to manage or understand these phenomena is critical to ensuring that we maintain a healthy planet capable of sustaining humanity as part of its diverse bio-mass.\u00a0 But understanding these phenomena and how they are changing over time requires measurement.<\/p>\n<p>&nbsp;<\/p>\n<h2>Perspective<\/h2>\n<p>The view from outside often provides unique insights into an environment as it can be extraordinarily difficult to objectively observe a system from within.\u00a0 Once the ability to \u201cslip the surly bonds of earth\u201d <sup>1 <\/sup>was established in the 1960\u2019s it quickly became a race for government sponsored space agencies to exploit the ability to observe our earth from above by deploying satellites with capabilities for earth observation (EO). From the first space-based multispectral imager (MSI), Landsat-1, launched by NASA in 1972, to the ESA\u2019s Sentinel-2B \u201cEurope\u2019s eyes on earth\u201d launched in 2017, to the planned GCOM-C launch from JAXA, table 1 illustrates just a few examples of the different optical EO instruments deployed to date.<\/p>\n<table>\n<tbody>\n<tr>\n<td width=\"49\"><strong>NASA<\/strong><\/td>\n<td width=\"318\">Landsat-1<\/td>\n<td width=\"227\">4 band (Green, Red, two NIR)<\/td>\n<td width=\"44\">1972<\/td>\n<\/tr>\n<tr>\n<td width=\"49\"><strong>\u00a0<\/strong><\/td>\n<td width=\"318\">JPSS; VIIRS (Visible IR Imaging Radiometer Suite)<\/td>\n<td width=\"227\">22 bands (412nm-12um); 1 PAN, 9 VIS\/NIR, 8 MWIR, 4 LWIR<\/td>\n<td width=\"44\">2011<\/td>\n<\/tr>\n<tr>\n<td width=\"49\">\u00a0<\/td>\n<td width=\"318\">GOES-16;\u00a0 ABI (Advanced Baseline Imager)<\/td>\n<td width=\"227\">16 bands (2 VIS; 4 NIR; 10 IR)<\/td>\n<td width=\"44\">2016<\/td>\n<\/tr>\n<tr>\n<td width=\"49\">\u00a0<\/td>\n<td width=\"318\">GOES-16;\u00a0 GLM (Geostationary Lightning Mapper)<\/td>\n<td width=\"227\">single NIR band imaging 777.4nm<\/td>\n<td width=\"44\">2016<\/td>\n<\/tr>\n<tr>\n<td width=\"49\"><strong>ESA<\/strong><\/td>\n<td width=\"318\">ERS-1; IRR (Infrared Radiometer)<\/td>\n<td width=\"227\">4 band MSI VIS-SWIR (650-1.6nm)<\/td>\n<td width=\"44\">1991<\/td>\n<\/tr>\n<tr>\n<td width=\"49\"><strong>\u00a0<\/strong><\/td>\n<td width=\"318\">Proba-V (vegetation)<\/td>\n<td width=\"227\">4 bands (Blue, Red, NIR, MWIR)<\/td>\n<td width=\"44\">2013<\/td>\n<\/tr>\n<tr>\n<td width=\"49\">\u00a0<\/td>\n<td width=\"318\">Copernicus \u2013 Sentinel-2B<\/td>\n<td width=\"227\">VIS\/SWIR MSI 443-2190nm<\/td>\n<td width=\"44\">2017<\/td>\n<\/tr>\n<tr>\n<td width=\"49\"><strong>ISRO<\/strong><\/td>\n<td width=\"318\">Rohini RS-D2<\/td>\n<td width=\"227\">VIS\/IR imaging<\/td>\n<td width=\"44\">1983<\/td>\n<\/tr>\n<tr>\n<td width=\"49\">\u00a0<\/td>\n<td width=\"318\">Oceansat(IRS-P4); OCM (Ocean Colour Monitor)<\/td>\n<td width=\"227\">8 band MSI VIS-IR<\/td>\n<td width=\"44\">1999<\/td>\n<\/tr>\n<tr>\n<td width=\"49\">\u00a0<\/td>\n<td width=\"318\">RESOURCESAT-2A<\/td>\n<td width=\"227\">4 band (3 VIS;\u00a0 NIR\/SWIR)<\/td>\n<td width=\"44\">2016<\/td>\n<\/tr>\n<tr>\n<td width=\"49\"><strong>JAXA<\/strong><\/td>\n<td width=\"318\">GCOM-C; SGLI (Second Generation Global Imager)<\/td>\n<td width=\"227\">19 bands; Near UV to LWIR (380nm-12um)<\/td>\n<td width=\"44\">Planned 2017<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Table 1. Examples of EO missions employing optical instruments<sup>2<\/sup><\/p>\n<p>However, observation from orbit has presented its own set of challengesand associated solutions:<\/p>\n<ul>\n<li>CHALLENGE: see through the atmosphere (clouds\/aerosols) or in some cases observe only these atmospheric constituents or phenomena\n<ul>\n<li>SOLUTION: wavelength selective imaging<\/li>\n<\/ul>\n<\/li>\n<li>CHALLENGE: observe small signals in a large background scene\n<ul>\n<li>SOLUTION: large, highly uniform collection optics<\/li>\n<\/ul>\n<\/li>\n<li>CHALLENGE: pack as much measurement capability into as small and lightweight a package as possible to reduce launch costs\n<ul>\n<li>SOLUTION: compact\/multi-spectral imaging<\/li>\n<\/ul>\n<\/li>\n<li>CHALLENGE: determine the type of phenomena (<em>\u201cwhat\u201d<\/em>) and location (<em>\u201cwhere\u201d<\/em>) under observation from a distance (eg. low earth orbit is 160-2000 km above the earth\u2019s surface)\n<ul>\n<li>SOLUTION: combination of high spatial (<em>\u201cwhere\u201d<\/em>) and spectral (<em>\u201cwhat\u201d<\/em>) resolution<\/li>\n<\/ul>\n<\/li>\n<li>CHALLENGE: survive launch conditions and operate outside of earth\u2019s protective atmospheric blanket\n<ul>\n<li>SOLUTION: robust and reliable optical components<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>Optical filters of different designs and formats are a key contributor to each of these solutions within photonics based EO instruments, serving as <strong><em>\u201cthe eyes of the instruments\u201d.<\/em><\/strong><\/p>\n<h2>\u00a0<\/h2>\n<h2>\u00a0<\/h2>\n<h2>Wavelength Selective Imaging<\/h2>\n<p>Whether one utilizesband-pass (BPF), notch, or edge-pass designs, by their nature optical filters provide wavelength selectivity to the instruments in which they are employed.\u00a0 In EO systems, single selective wavelength bands are often necessary to allow observation of unique spectral characteristics representative of specific phenomena of interest.\u00a0 Different atmospheric and environmental constituents have different wavelength bands that are reflected, transmitted, or absorbed dependent on their chemical composition.\u00a0 The table below shows the optical bands on NASA\u2019s Landsat 8 and how they relate to the constituents being measured.<\/p>\n<table>\n<tbody>\n<tr>\n<td width=\"61\">Band #<\/td>\n<td width=\"102\">Wavelength range (nm)<\/td>\n<td width=\"108\">Spatial Resolution (m)<\/td>\n<td width=\"318\">Constituent Measured<\/td>\n<\/tr>\n<tr>\n<td width=\"61\">1<\/td>\n<td width=\"102\">433-453<\/td>\n<td width=\"108\">30<\/td>\n<td width=\"318\">Coastal (shallow water)\/aerosol (fine dust\/smoke)<\/td>\n<\/tr>\n<tr>\n<td width=\"61\">2<\/td>\n<td width=\"102\">450-515<\/td>\n<td width=\"108\">30<\/td>\n<td width=\"318\">Visible (blue)<\/td>\n<\/tr>\n<tr>\n<td width=\"61\">3<\/td>\n<td width=\"102\">525-600<\/td>\n<td width=\"108\">30<\/td>\n<td width=\"318\">Visible (green)<\/td>\n<\/tr>\n<tr>\n<td width=\"61\">4<\/td>\n<td width=\"102\">630-680<\/td>\n<td width=\"108\">30<\/td>\n<td width=\"318\">Visible (red)<\/td>\n<\/tr>\n<tr>\n<td width=\"61\">5<\/td>\n<td width=\"102\">845-885<\/td>\n<td width=\"108\">30<\/td>\n<td width=\"318\">NIR \u2013 vegetation<\/td>\n<\/tr>\n<tr>\n<td width=\"61\">6<\/td>\n<td width=\"102\">1556-1660<\/td>\n<td width=\"108\">30<\/td>\n<td width=\"318\">Geology \u2013 Earth, soils and rocks<\/td>\n<\/tr>\n<tr>\n<td width=\"61\">7<\/td>\n<td width=\"102\">2100-2300<\/td>\n<td width=\"108\">30<\/td>\n<td width=\"318\">Geology \u2013 Earth, soils and rocks<\/td>\n<\/tr>\n<tr>\n<td width=\"61\">8<\/td>\n<td width=\"102\">500-680<\/td>\n<td width=\"108\">15<\/td>\n<td width=\"318\">PAN<\/td>\n<\/tr>\n<tr>\n<td width=\"61\">9<\/td>\n<td width=\"102\">1360-1390<\/td>\n<td width=\"108\">30<\/td>\n<td width=\"318\">Clouds<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Table 2. Landsat 8 optical bands <em>[Ref NASA]<\/em><\/p>\n<p>By selecting optical filters with a band-pass region corresponding to the wavelength band of interest the user can then selectively observe only the signal from the constituent or phenomena under study gaining \u201cmore signal with less background\u201d in their data.<\/p>\n<h2>\u00a0<\/h2>\n<h2>\u00a0<\/h2>\n<h2>\u00a0<\/h2>\n<h2>Large, Highly Uniform Collection Optics<\/h2>\n<p>If the constituent of interest has spectral bands that are very narrow or are in close spectral proximity to \u201cbackground\u201d bands or if the signal is a small contributor compared to the background, then large, narrow band-pass filters (NBPFs) providing enhanced wavelength selectivity may be required.<\/p>\n<p>Measuring or mapping lightning from orbitis an example of application demanding high wavelength selectivity over a large field of view.\u00a0 Lightning can be studied by observing a narrow atomic oxygen triplet line at 777.4nm.\u00a0 However, as it uncertain as to where and when a lightning strike may occur a large detector area is needed over which this very narrow wavelength selectivity is maintained.\u00a0 This requires an extremely uniform, narrow optical filter.\u00a0 Iridian has demonstrated the capability to produce such a NBPF centered to within 20pm of the target wavelength over an operating clear aperture &gt;125mm in diameter<sup>3<\/sup>.<\/p>\n<\/div>\n<\/div>\n<p>[\/et_pb_text][et_pb_text admin_label=&#8221;Single Band Filters&#8221; _builder_version=&#8221;4.4.8&#8243; global_colors_info=&#8221;{}&#8221;]<\/p>\n<p><span style=\"color: #3366ff;\"><strong>Single Band Filters<\/strong><\/span> enable the receiver (imager\/detector) to selectively receive a specific wavelength band of interest. An example is ESA\u2019s Meteosat Third Generation (MTG) lightning imager instrument selectively detecting an oxygen triplet absorption line at 777.4nm by use of a highly uniform,\u00a0 narrow BPF optical filter.<\/p>\n<p>(The above mentioned NBPF has been developed under a contract with Leonardo S.p.a for the Lightning Imager Instrument, in the frame of the ESA program Meteosat Third Generation (MTG).<\/p>\n<p>Typical BPF requirements include:<\/p>\n<ul>\n<li>narrow passband regions with high transmittance (Tx)<\/li>\n<li>deep and broad out of band blocking\n<ul>\n<li>steep edges provide a sharp transition from Tx to blocking<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<ul>\n<li>high uniformity (these filters are often (up to 150mm diameter)<\/li>\n<li>excellent transmitted wavefront error and surface quality\n<ul>\n<li>preserves image integrity<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<ul>\n<li>robust to survive in orbit (solar radiation durability)\u00a0<\/li>\n<\/ul>\n<p>[\/et_pb_text][et_pb_image src=&#8221;https:\/\/iridian.com.cn\/wp-content\/uploads\/2017\/09\/BPF-Image-1024&#215;708.png&#8221; align=&#8221;center&#8221; admin_label=&#8221;chart&#8221; _builder_version=&#8221;4.4.3&#8243; width=&#8221;75%&#8221; global_colors_info=&#8221;{}&#8221;][\/et_pb_image][et_pb_text _builder_version=&#8221;4.4.3&#8243; text_font_size=&#8221;11px&#8221; text_orientation=&#8221;center&#8221; global_colors_info=&#8221;{}&#8221;]<\/p>\n<p>Figure 1.Spatial variation in CWL across 125mm diameter demonstrating highly uniform large NBPF<\/p>\n<p>[\/et_pb_text][et_pb_image src=&#8221;https:\/\/iridian.com.cn\/wp-content\/uploads\/2020\/06\/narrow-bpf.png&#8221; title_text=&#8221;narrow bpf&#8221; align=&#8221;center&#8221; admin_label=&#8221;chart2&#8243; _builder_version=&#8221;4.4.8&#8243; width=&#8221;75%&#8221; module_alignment=&#8221;center&#8221; global_colors_info=&#8221;{}&#8221;][\/et_pb_image][et_pb_text _builder_version=&#8221;4.4.8&#8243; global_colors_info=&#8221;{}&#8221;]<\/p>\n<h3><span style=\"color: #3366ff;\"><strong>Space Heritage<\/strong><\/span><\/h3>\n<p>Iridian has produced individual filters and multi-spectral elements that have been tested and qualified for a range of orbits and space environments. Iridian is a registered participant in the Canadian Controlled Goods Program.<\/p>\n<p>Examples of space environment testing and qualification that our filters have passed include:<\/p>\n<ul>\n<li>Radiation exposure (gamma rays, protons, combined solar UV and electrons)<\/li>\n<li>Thermal cycling\/shock\/survivability including liquid N<sub>2<\/sub> to boiling ethanol dips<\/li>\n<li>Vibration testing<\/li>\n<li>Laser damage testing in excess of 1 MW\/cm<sup>2<\/sup><\/li>\n<li>Thermal vacuum cycling testing from 50K to 450K<\/li>\n<li>Outgassing testing as per ASTM-E595<\/li>\n<li>Reliability as per MIL-C-48497A<\/li>\n<\/ul>\n<p>Iridian has over 20 years of experience producing industry leading optical telecommunication and datacom filters for terrestrial systems. This communication filter expertise is combined with a space heritage providing filters flown in satellite applications such as earth observation and is supported by a dedicated Aerospace and Specialty Optics group to guide customers from initial specification and design through to full volume production from our Ottawa, Canada facility.<\/p>\n<p>[\/et_pb_text][et_pb_text disabled_on=&#8221;on|on|on&#8221; _builder_version=&#8221;4.4.3&#8243; disabled=&#8221;on&#8221; global_colors_info=&#8221;{}&#8221;]<\/p>\n<div class=\"et_pb_module et_pb_text et_pb_text_1  et_pb_text_align_left et_pb_bg_layout_light\">\n<div class=\"et_pb_text_inner\">\n<p>The advantage of an instrument with this precision and \u201cfield of view\u201d must be traded off against the increased weight and cost to produce such large complex filters and the optical components used in conjunction with them.<\/p>\n<h2>\u00a0<\/h2>\n<h2>Compact\/Multi-spectral Imaging<\/h2>\n<p>To minimize the weight and cost per \u201cscience line\u201d many EO imaging systems try to pack as much science into one instrument as possible by using a single detector to interrogate multiple spectral bands of interest.This multi-spectral imaging (MSI) has driven the need for filter arrays in which the spectral performance varies spatially across the part.<\/p>\n<\/div>\n<\/div>\n<div class=\"et_pb_module et_pb_image et_pb_image_1\"><span class=\"et_pb_image_wrap \"><img decoding=\"async\" class=\"aligncenter\" title=\"\" src=\"https:\/\/iridian.com.cn\/wp-content\/uploads\/2017\/09\/mlwir-filter-array-curves-1.jpg\" sizes=\"(max-width: 536px) 100vw, 536px\" srcset=\"https:\/\/iridian.com.cn\/wp-content\/uploads\/2017\/09\/mlwir-filter-array-curves-1.jpg 536w, https:\/\/iridian.com.cn\/wp-content\/uploads\/2017\/09\/mlwir-filter-array-curves-1-510x164.jpg 510w, https:\/\/iridian.com.cn\/wp-content\/uploads\/2017\/09\/mlwir-filter-array-curves-1-300x96.jpg 300w\" alt=\"\" \/><\/span><\/div>\n<div class=\"et_pb_module et_pb_text et_pb_text_2  et_pb_text_align_left et_pb_bg_layout_light\">\n<div class=\"et_pb_text_inner\">\n<p>Figure 2. Multi-spectral array of 10 BPFs (developed under a subcontract from ABB Canada for the Space Technology Development Program of the Canadian Space Agency)<\/p>\n<p>By using a filter with this type of construction, different pixel bands on the detector will be sensitive to different spectral bands and therefore different constituents or phenomena of interest.<\/p>\n<p>Manufacture of multi-zone\/multi-spectral filter (MZF or MSF) arrays can be achieved either via a butcher block construction, in which different filters are manufactured, singulated, and then assembled together into an array, or by patterning (via masking) different spectral bands on a monolithic substrate.<\/p>\n<p>Butcher block MZF arrays provide the advantage of simplifying the coating process by avoidance of compounding coating run yields; the filter manufacturer only coats a single band on any given substrate which is the approach used for most \u201cstandard\u201d optical filter manufacturing.\u00a0 Butcher block arrays can be a good choice when many (&gt;4 or 5) bands of interest are to be studied or when the complexity of individual filter bands is high, driving increased filter coating thickness and decreased run success yields.<\/p>\n<p>Patterned MZF arrays provide the possibility to create nearly any size or shape of spectral band (they don\u2019t need to be stripes or rectangles as in a butcher block) with substantial improvement (2x or more) in the size transition zone. Pixels under the transition zone are unusable for analysis so reducing theloss of good pixels by using a patterned array can be advantageous.\u00a0 Additionally, coating on monolithic substrates avoids challenges associated with alignment tolerances between the different spectral bands.<\/p>\n<p>&nbsp;<\/p>\n<h2>High Spatial and Spectral Resolution<\/h2>\n<p>Greater discrimination of a \u201cscience line\u201d can be enhanced by reducing the bandwidth of the filter associated with the band of interest. In MSI applications, this improvement in spectral resolution comes at the cost of reduced spatial resolution as this effectively shrinks the signal to noise (less total light) and the aperture size (pixels available) for any one band.\u00a0\u00a0 In contrast if a broad band, panchromatic (PAN) filter spanning the entire visible spectrum is used then the increase in total light at these pixels provides improved spatial resolution.\u00a0 For Landsat 8 the PAN band has twice the spatial resolution (15m versus 30m) compared to the other optical bands (see Table 2). By combining PAN along with wavelength selective bands,through \u201cpan sharpening\u201d an array can be used both to accurately map where specific signal is originating and what the signal represents.<\/p>\n<h2>\u00a0<\/h2>\n<h2>Robust and Reliable Optics<\/h2>\n<p>Finally, there is no value in having a system with a high resolution optical filter if it doesn\u2019t survive use in orbit.\u00a0 With careful control of deposition processes (sputtering or enhanced evaporating) and materials, experienced manufacturers can produce optical filters with good density and adhesion to withstand typical terrestrial requirements for variations in temperature and humidity without changing or degrading with use or over time.<\/p>\n<p>Typical reliability specs include:<\/p>\n<ul>\n<li>No change in spectral performance or degradation in surface quality after\n<ul>\n<li>24 hours of damp heat exposure (95%RH; 49 \u00b0C)).<\/li>\n<li>Thermal cycling\/shock tests from -60 to 70 \u00b0C<\/li>\n<\/ul>\n<\/li>\n<li>Tape and rub tests for adhesion<\/li>\n<\/ul>\n<p>Once in orbit these filters and filter arrays may also need to withstand extreme temperature ranges (down to 70 K) and the solar and electron radiation that is normally filtered out by our atmosphere.\u00a0 Filters and filter arrays used in these environments may require additional specialized testing to verify that they will survive in this harsh environment.<\/p>\n<p>&nbsp;<\/p>\n<h2>Challenges for the Future<\/h2>\n<p>As launch costs continue to decline the commercialization of space isproliferating.\u00a0 While NASA, ESA, and ISRO continue to plan and to launch satellites with EO capabilities, more and more we can expect that constellations of EO satellites will be owned and operated by private organizations such as Planet, Urthecast, Satellogic, and BlackSky Global, rather than governmental space agencies.\u00a0 In the \u201c<em>2016 Nano\/Microsatellite Market Forecast\u201d<\/em> SpaceWorks forecasted that from 2018-2020 there will be ~1000 nano\/microsatellite (1-50kg) launches, 70% of which will be commercial rather than government projects.\u00a0 More than 70% of these projects are expected to be intended for EO applications (up from &lt;40% EO projects over the past half-decade).<\/p>\n<p>This capitalism of space will make more information available than ever before and this data will be used for more than just the historical defense and intelligence \u201cbig brother\u201d purposes.\u00a0 Once the flow of extra-terrestrially gathered data opens up, new applications are sure to emerge to leverage this information to better manage and control terrestrial activities and commerce.\u00a0\u00a0 Photonics and optical filtersare poised to play a key role in enabling many of these new developments.<\/p>\n<ul>\n<li><em>[Ref. John Gillespie Magee, Jr.]<\/em><\/li>\n<li><em>[Ref NASA,ESA,ISRO,JAXA]<\/em><\/li>\n<li><em>Large format BPF \u2013 a uniformity challenge (Iridian)<\/em><\/li>\n<\/ul>\n<\/div>\n<\/div>\n<p>[\/et_pb_text][\/et_pb_column][\/et_pb_row][\/et_pb_section][et_pb_section fb_built=&#8221;1&#8243; disabled_on=&#8221;on|on|on&#8221; _builder_version=&#8221;4.3.4&#8243; custom_margin=&#8221;||75px||false|false&#8221; disabled=&#8221;on&#8221; global_colors_info=&#8221;{}&#8221;][et_pb_row column_structure=&#8221;1_4,3_4&#8243; _builder_version=&#8221;4.3.4&#8243; global_colors_info=&#8221;{}&#8221;][et_pb_column type=&#8221;1_4&#8243; _builder_version=&#8221;4.3.4&#8243; global_colors_info=&#8221;{}&#8221;][\/et_pb_column][et_pb_column type=&#8221;3_4&#8243; _builder_version=&#8221;4.3.4&#8243; global_colors_info=&#8221;{}&#8221;][et_pb_button button_url=&#8221;\/rfq\/&#8221; url_new_window=&#8221;on&#8221; button_text=&#8221;@ET-DC@eyJkeW5hbWljIjp0cnVlLCJjb250ZW50IjoicG9zdF90aXRsZSIsInNldHRpbmdzIjp7ImJlZm9yZSI6IkNvbnRhY3QgVXMgZm9yIFlvdXIgIiwiYWZ0ZXIiOiIgUmVxdWlyZW1lbnRzIn19@&#8221; button_alignment=&#8221;left&#8221; admin_label=&#8221;CTA button- Contact us&#8221; _builder_version=&#8221;4.3.4&#8243; _dynamic_attributes=&#8221;button_text&#8221; global_colors_info=&#8221;{}&#8221;][\/et_pb_button][\/et_pb_column][\/et_pb_row][\/et_pb_section]<\/p>\n","protected":false},"excerpt":{"rendered":"<p>The view from outside often provides unique insights into an environment as it can be extraordinarily difficult to objectively observe a system from within.\u00a0 Once the ability to \u201cslip the surly bonds of earth\u201d was established in the 1960\u2019s it quickly became a race to exploit the ability to observe our earth from above by [&hellip;]<\/p>\n","protected":false},"author":159,"featured_media":0,"parent":0,"menu_order":42,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"_et_pb_use_builder":"on","_et_pb_old_content":"","_et_gb_content_width":"","footnotes":""},"class_list":["post-15592","page","type-page","status-publish","hentry"],"acf":[],"_links":{"self":[{"href":"https:\/\/iridian.com.cn\/en\/wp-json\/wp\/v2\/pages\/15592","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/iridian.com.cn\/en\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/iridian.com.cn\/en\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/iridian.com.cn\/en\/wp-json\/wp\/v2\/users\/159"}],"replies":[{"embeddable":true,"href":"https:\/\/iridian.com.cn\/en\/wp-json\/wp\/v2\/comments?post=15592"}],"version-history":[{"count":4,"href":"https:\/\/iridian.com.cn\/en\/wp-json\/wp\/v2\/pages\/15592\/revisions"}],"predecessor-version":[{"id":20414,"href":"https:\/\/iridian.com.cn\/en\/wp-json\/wp\/v2\/pages\/15592\/revisions\/20414"}],"wp:attachment":[{"href":"https:\/\/iridian.com.cn\/en\/wp-json\/wp\/v2\/media?parent=15592"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}