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Accurate Establishment of Error Models for the Satellite Gravity Gradiometry Recovery and Requirements Analysis for the Future GOCE Follow-On Mission

Zheng W., Wang Z., Ding Y., Li Z.

Acta Geophysica

2016

Vol. 64, no. 3

732--754

Firstly, the new single and combined error models applied to estimate the cumulative geoid height error are efficiently produced by the dominating error sources consisting of the gravity gradient of the satellite-equipped gradiometer and the orbital position of the space-borne GPS/GLONASS receiver using the power spectral principle. At degree 250, the cumulative geoid height error is 1.769 × 10–1 m based on the new combined error model, which preferably accords with a recovery accuracy of 1.760 × 10–1 m from the GOCE-only Earth gravity field model GO_CONS_GCF_2_TIM_R2 released in Germany. Therefore, the new combined error model of the cumulative geoid height is correct and reliable in this study. Secondly, the requirements analysis for the future GOCE Follow-On satellite system is carried out in respect of the preferred design of the matching measurement accuracy of key payloads comprising the gravity gradient and orbital position and the optimal selection of the orbital altitude of the satellite. We recommend the gravity gradient with an accuracy of 10–13-10–15 /s2 , the orbital position with a precision of 1-0.1 cm and the orbital altitude of 200-250 km in the future GOCE Follow-On mission.

Influence of junction temperature on the spectral power distribution of Light Emitting Diodes

Budzyński Ł

Challenges of Modern Technology

2015

Vol. 6, no. 4

3--7

This article describes electrical method for measuring junction temperature of high power LEDs. Measurement system consisting of a temperature controller and a thermostatic chamber was designed and constructed. A number of studies of LEDs in a typical thermal conditions that exist in luminaries were performed. Basing on these results, influence of junction temperature on luminous flux and spectral power distribution of LED was determined. Obtained results allow to optimize the construction of LED lighting fixtures, in the ambient temperature range from 0°C to 100°C, especially in the aspect of improving the photometric properties of the luminaire.