Planet’s mission is to image the entire Earth, every day, and make global change visible, accessible, and actionable. Planet designs, builds and launches satellites faster than any company or government in history, now operating the largest network of diversified and disaggregated sensors in orbit. Planet relies on quick iterations and space-based testing of satellites, optics, software and systems to create increasingly technology-dense and cost-effective spacecraft.
Planet owns and operates fleets of over 100 Dove satellites capturing the whole earth land surface every day at 3.9m with 4 spectral bands (blue, green, red, nir), 5 RapidEye satellites capturing up to 7Mio Sqkm of land surface at 6.5m with 5 spectral bands and 13 SkySat satellites capturing 51k sqkm of earth surface at 0.72m gsd.
The proposed presentation will show the full on-orbit radiometric calibration process for the SkySat constellation. This calibration includes the creation of per detector correction gain and offset tables serving the correction of non uniform response of the individual detectors. Additionally the procedures and results for the conversion of raw DN counts into absolute calibrated top of atmosphere radiance products will be shown. The latter shows the application of vicarious calibration methods based on the RadCalNet network of automated calibration sites and cross calibration between the individual satellites of the constellation, other planet owned constellations (especially RapidEye) and other available satellites like e.g. Landsat8
The concept of exponential averaging of a reconstructed wavefront is extended by considering the full process of image formation in digital holographic microscopy (DHM), including object illumination, optical imaging, reference wave, and hologram sampling. Phase filtering by exponential averaging uses the whole capability of DHM to retrieve both the amplitude and phase of a wavefront. The aim is to apply the exponential filtering to the spatial distribution of the complex reflection coefficient of the object surface rather than to the whole orthoscopically reconstructed wavefront. To identify possible contributions to errors in the weighting of the exponential averaging, the phase measurement process of DHM is described as a signal transmission path. Accordingly, the orthoscopic wavefront needs to be compensated for both amplitude and phase of the illuminating wave and of the reference wave as closely as possible. As hologram sampling can introduce spectral amplitude attenuation, its numerical compensation is also proposed. Finally, nonlinear amplitude weighting is proposed in exponential averaging. For a better understanding of the physical meaning of weighting and its particular importance for measuring rough object surfaces, the effect of object roughness on an imaged object wavefront is presented by the concept of optical convolution.
Radiometric calibration of the RapidEye Multispectral Imager (MSI) and other remote sensing imaging systems is an essential task in the quantitative assessment of sensor image quality and the production of reliable data products for a wide range of geo-spatial applications. Spatially and temporally pseudo-invariant terrestrial targets have long been used to characterize Earth observation systems and provide a consistent record of their radiometric performance. This study focuses on the use of near-simultaneous acquisitions of calibration test sites by all of the RapidEye Multispectral Imagers (MSI) as a means to track the relative radiometric stability of the five sensors in the constellation. As the cameras acquired the sites with different image acquisition and solar illumination parameters, a compensation factor is derived to account for the site bidirectional-reflectance-function (BRDF) variations that occur with different sun-target-sensor acquisition conditions. The derived top-of-atmosphere reflectance is computed as a figure of merit to measure and track the constellation response to each of the test sites. The results show that the differences between the same bands on the different spacecraft are much smaller than what BlackBridge promises in the RapidEye product specifications.
Digital holography has proven its ability to acquire high accuracy full field 3D data with one single image acquisition. This means that in principle this technique offers the chance to perform 3D serial inspection processes, as well. However, one limitation in digital holography is its limited ability to measure rough surfaces. In the presence of rough surfaces, the magnification of the image has to be increased to capture the required phase information on each camera pixel. However, this leads to significant reduction of inspection speed. If low magnification is selected, the rough surface produces speckles which cannot be treated properly by digital holography algorithms. In this paper, we describe the extension of digital holography to rough surface applications using speckle interferometry technique. This technique is capable of fast inspection of rough surfaces with sub-micrometer accuracy. The principle of this approach is shown and a practical application for 3D surface inspection of wafer cutting processes is given.
RapidEye AG is a commercial provider of geo-spatial information products derived from Earth observation image data.
The source of this data is the RapidEye constellation of five low-earth-orbit imaging satellites. Image data from satellite
electro-optical sensors contains spatial artifacts such as banding and streaking that are caused by detector responsivity
variations, factors related to image formation, and the space environment. This paper describes the results of a relative
radiometric calibration and correction campaign that was conducted between March and July 2011 using the side-slither
technique. Radiometrically uniform terrestrial scenes that included desert and snow/ice regions were imaged with a
RapidEye sensor in a ninety-degree yaw orbital configuration. In this configuration each detector on the focal plane was
positioned parallel to the ground-track direction thereby exposing each detector to the light reflected from the same
segment of the ground. This maneuver produced a radiometrically flat-field input to the sensor so that the relative
response of each detector was determined for the same exposure level. Side-slither derived detector correction
parameters were then used to improve the quality of RapidEye imagery that contained noticeable spatial artifacts. A
significant improvement in image correction was achieved when compared to our standard correction procedures.
During the MINEO flight-campaign in summer 2000 HyMap data was recorded for the test site Kirchheller Heide north of the Ruhr district. The aim of this project is to use hyperspectral spectrometer data to detect environmental and ecological changes. They are caused by an affected hydrological balance due to deep hard coal mining. Dynamic mining demands regular updates of the spatial information. This data will become part of an environmental monitoring system which shall comprise analysis of hyperspectral data as an important constituent. As an essential preprocessing step for vegetation studies and multitemporal analyses, ATCOR-4 was used for atmospheric correction. Additionally, atmospheric data from Deutscher Wetterdienst (DWD) and ground reflectance spectra were recorded as an essential data-input for the ATCOR 4 model. The field spectra were used first to control the accuracy of the standard calibration files which are provided with the hyperspectral data. This workflow provides accurate results for wavelengths shorter than 1 micrometers directly. In an interactive manner the inflight calibration module of ATCOR-4 allows to built up and adapt new calibration files suitable for all wavelengths. The first calculated atmospheric lookup-tables and this final calibration file were used to perform the atmospheric correction for the HyMap scene.
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