The Jiao Tong University Spectroscopic Telescope Project

The Jiao Tong University Spectroscopic Telescope(JUST)is a 4.4-meter f/6.0 segmented-mirror telescope dedicated to spectroscopic observations.The JUST primary mirror is composed of 18 hexagonal segments,each with a diameter of 1.1 m.JUST provides two Nasmyth platforms for placing science instruments.One Nasmyth focus fits a field of view of 10′and the other has an extended field of view of 1.2°with correction optics.A tertiary mirror is used to switch between the two Nasmyth foci.JUST will be installed at a site at Lenghu in Qinghai Province,China,and will conduct spectroscopic observations with three types of instruments to explore the dark universe,trace the dynamic universe,and search for exoplanets:(1)a multi-fiber(2000 fibers)medium-resolution spectrometer(R=4000-5000)to spectroscopically map galaxies and large-scale structure;(2)an integral field unit(IFU)array of 500 optical fibers and/or a long-slit spectrograph dedicated to fast follow-ups of transient sources for multi-messenger astronomy;(3)a high-resolution spectrometer(R~100000)designed to identify Jupiter analogs and Earth-like planets,with the capability to characterize the atmospheres of hot exoplanets.

Volunteered remote sensing data generation with air passengers as sensors

Remote sensing satellites are playing very important roles in diverse earth observation fields.However,long revisit period,high cost and dense cloud cover have been the main limitations of satellite remote sensing for a long time.This paper introduces the novel volunteered passenger aircraft remote sensing(VPARS)concept,which can partly overcome these problems.By obtaining aerial imaging data from passengers using a portable smartphone on a passenger aircraft,it has various advantages including low cost,high revisit,dense coverage,and partial anti-cloud,which can well complement conventional remote sensing data.This paper examines the concept of VPARS and give general data processing framework of VPARS.Several cases were given to validate this processing approach.Two preliminary applications on land cover classification and economic activity monitoring validate the applicability of the VPARS data.Furthermore,we examine the issues about data maintenance,potential applications,limitations and challenges.We conclude the VPARS can benefit both scientific and industrial communities who rely on remote sensing data.

Investigating the seasonal dynamics of surface water over the Qinghai-Tibet Plateau using Sentinel-1 imagery and a novel gated multiscale ConvNet

The surface water in the Qinghai–Tibet Plateau(QTP)region has undergone dramatic changes in recent decades.To capture dynamic surface water information,many satellite imagery-based methods have been proposed.However,these methods are still limited in terms of automation and accuracy and thus prevent surface water dynamic studies in large-scale QTP regions.In this study,we developed a new fully automatic method for accurate surface water mapping by using Sentinel-1 synthetic aperture radar(SAR)imagery and convolutional networks(ConvNets).Specifically,we built a new multiscale ConvNet structure to improve the model capability in surface water body extraction.Moreover,a gating mechanism is introduced to promote the efficient use of multiscale information.According to the accuracy assessment,the proposed gated multiscale ConvNet(GMNet)achieved the highest overall accuracy of 98.07%.We applied our GMNet for monthly surface water mapping on the QTP;accordingly,we found that the QTP region experienced significant surface waterfluctuations over one year.The surface water also showed distinct spatial heterogeneity on the QTP;that is,the surface water fraction of the Inner Tibetan Basin was significantly higher than that of the Mekong Basin in both the wet and dry seasons.