In-orbit optical performance assessment of Geostationary Ocean Color Imager
After Geostationary Ocean Color Imager (GOCI) was launched at June 27th, 2010, it is operated to observe the Korean peninsula on the geostationary orbit as one of the three main payloads in COMS satellite. Generally, the performance indicators are Ground Sample Distance (GSD), Modulation Transfer Function (MTF), and Signal to Noise Ratio (SNR) that verify the optical performance of payload. Most of all, the MTF performance is widely used since it is closely related to reliability and accuracy of observational target information in aspects of satellite image application. Especially, in case of ocean color sensor, for confirming the ability of GOCI to separate the slight difference of ocean color information, on-orbit MTF performance test and SNR assessment should be performed.
SNR CALCULATION METHOD FOR REMOTE SENSING SATELLITE IMAGING SYSTEMS
Sinyal Gurultu Orani (SGO) uydu goruntuleme sistemlerinde goruntu kalitesi ile radyometrik performansi birbirine baglayan bir olcut olarak kullanilir ve uzaktan algilama uydu goruntuleme sistemlerinde goruntu kalitesini gosteren parametrelerden birisidir. Uzaktan algilama uydu goruntu sistemi tasarim asamasinda SGO hesaplamalarinin ve analizlerinin yapilmasi gerekmektedir. Bu hesaplama ve analiz calismalari tasarima yon verilmesi ve tasarimin dogrulanmasi icin onem tasimaktadir. Tasarlanan optik goruntuleme sistemine kaliteli bir goruntu olusturabilecek isik akisinin ulastigi ve ulasan bu isik akisinin sensor uzerinde yeteri kadar elektron olusturdugu gosterilmelidir. Bu calismada alcak irtifa yorungesinde gorev alan yakin kizil otesi bantta calisan bir uydu goruntuleme sisteminin spektral ve toplam isik aki miktari hesaplamasi yapilarak SGO analizi sunulmustur. Optik sistemin goruntu kalitesinin tasarim asamasinda tahmin edilebilmesi ve optik giris aciklik capinin belirlenmesi icin sensore gelen isik miktarinin hesaplanmasi ve SGO analizinin yapilmasi gerekmektedir. Bu calismada uzaktan algilama uydu goruntuleme sistemleri icin yer yuzunden yansiyip atmosferi gecerek goruntuleme sensorunun bir pikseline olusan toplam elektron sinyal miktari hesaplama yontemi verilmis ve SGO analizi yapilmistir. Onerilen SGO analiziyle optik goruntuleme sisteminin 2,5 milisaniye goruntu alma suresince dusuk kapasitans modda calistirilmasiyla sensorun bir pikselinin %28,2'i elektronlarla doldugu, kazancin 0,56 V ve SGO'nin 861 oldugu tespit edilmistir.
Long Ceramic Beam Tubes for Accelerator Magnets
The ceramic beam tubes for the fast and abort kickers and the bucker and pinger magnets used at Fermilab must meet a number of exacting requirements. The tubes must be long and sufficiently straight so as not to limit magnet design. They must have wall strength capable of withstanding the atmospheric and mechanical forces encountered during construction and operation. Vacuum tight ceramic to stainless steel transitions must be of reasonable cost; they must also withstand high temperature processing and remain vacuum tight to the 10/sup -9/ Torr range. To remove the possibility of static charge buildup each tube must have a surface coating of indium oxide applied to the inner wall. This thin coating is difficult to achieve and requires the most careful attention to detail. The methods used at Fermilab to achieve these goals are presented in this paper.