This paper presents details of the SkySat-1 mission, which is the first microsatellite-class commercial earthobservation system to generate sub-meter resolution panchromatic imagery, in addition to sub-meter resolution 4-band pan-sharpened imagery. SkySat-1 was built and launched for an order of magnitude lower cost than similarly performing missions. The low-cost design enables the deployment of a large imaging constellation that can provide imagery with both high temporal resolution and high spatial resolution.One key enabler of the SkySat-1 mission was simplifying the spacecraft design and instead relying on groundbased image processing to achieve high-performance at the system level. The imaging instrument consists of a custom-designed high-quality optical telescope and commercially-available high frame rate CMOS image sensors. While each individually captured raw image frame shows moderate quality, ground-based image processing algorithms improve the raw data by combining data from multiple frames to boost image signal-to-noise ratio (SNR) and decrease the ground sample distance (GSD) in a process Skybox calls "digital TDI". Careful quality assessment and tuning of the spacecraft, payload, and algorithms was necessary to generate high-quality panchromatic, multispectral, and pan-sharpened imagery. Furthermore, the framing sensor configuration enabled the first commercial High-Definition full-frame rate panchromatic video to be captured from space, with approximately 1 meter ground sample distance.Details of the SkySat-1 imaging instrument and ground-based image processing system are presented, as well as an overview of the work involved with calibrating and validating the system. Examples of raw and processed imagery are shown, and the raw imagery is compared to pre-launch simulated imagery used to tune the image processing algorithms.
Thirty-six patients with pagetic involvement of the spine were evaluated clinically and by computed tomography (CT). Pagetic phase, modeling expansion, degree and site of spinal stenosis, and pagetic facet joint arthropathy were recorded for each involved vertebral segment. CT demonstrated spinal stenosis in 20 patients, 11 of whom exhibited spinal stenosis on plain films. Twenty-one patients had symptoms of neck or back pain, with associated neurologic dysfunction in 13. Spinal stenosis was present in 81% of the symptomatic patients and 20% of the asymptomatic patients. Severe pagetic facet arthropathy was present in 17 of the symptomatic patients. We conclude that spinal stenosis is an important cause of vertebral pain and neurologic dysfunction.
Perforators arising from the first and fourth LAs arise in a predictable fashion, have adequate pedicle lengths, and are of suitable diameter to support a perforator flap. We present a case to support the potential use of this flap for microvascular breast reconstruction.
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