Total Solar Irradiance (TSI) has been recorded daily by Total Solar Irradiance Monitors (TSIM) with overlapping
measurements on FY-3 (Feng Yun-3) series satellites since 2008. Instrument descriptions, operation in space and flight
performance of three TSIMs are presented in this paper. TSI is measured by electrical substitution radiometers integrated
in TSIM, with traceability to SI. TSIM/FY-3A and TSIM/FY-3B share nearly the same design. Since TSIM/FY-3A and
TSIM/FY-3B have no pointing system, the Sun is only observed when the Sunlight sweeps TSIM’s field-of-view and
TSI measurements are influenced inevitably by solar pointing errors. TSIM/FY-3C, a radiometer package was
constructed with a pointing system for solar tracking in order to achieve accurate solar pointing. TSIM/FY-3C was sent
into orbit in September 2013 onboard FY-3C satellite. Daily TSI measurements have been performed by TSIM/FY-3C
with autonomous accurate solar tracking for 1 year. TSIM/FY-3C is in a good instrument health according to its on-orbit
A new shape of blackbody cavity composed of a conical generatrix and a flat inclined bottom is developed for absolute optical radiation measurement in space. For the new-shape cavity with specular isothermal cavity walls, the Monte Carlo method was used to obtain the optimal cavity geometrical parameters, such as the conical angle and inclination angle of the bottom. Distribution maps of the number of reflections over the aperture for traced rays were depicted for demonstrating the performance of the new cavity. Finally, the new-shape cavity was simulated as a blackbody absorber in cryogenic solar absolute radiometer (CSAR). Calculation results reflect that the new-shape cavity can get high absorptivity and achieve high accuracy measurements in CSAR from space.
In order to improve the wavelength utilization as well as the fairness of the light trail
networks, we modified the FP MAC from the view point of weight balance by introducing a
weight mode. The weight mode is composed of two factors, real-time factor and node activity
ratio. Moreover, the weight mode is used as a bid by each LT node to compute the priority.
Hence, the priority of the LT node is adjusted dynamically in every round and the MAC
protocol with dynamic priority adjustment is entitled as DPA MAC. Simulation results show
that the performances of DPA MAC protocol are much better than that of FP MAC protocol
in terms of packet loss rate and activity percentile.
STIM (Solar Total Irradiance Monitor) can be used on sun-synchronous polar orbit weather satellites to measure the total solar irradiance. It contains three independent and identical wide view absolute radiometers. They are mounted on the satellite in an angle which ensure the sun scan over the field of view of the absolute radiometers. This measurement method doesn't need the instrument tracking the sun but the sun scan over the field of view of the absolute radiometers in each orbit cycle. The paper presents the measurement method of simulation for solar irradiance measurement and calibration by mounting the instrument on a two-axis rotation table. By controlling the rotation angle velocity of the instrument in the meridian direction being the same as that of the weather satellite's on orbit, we can measure the solar irradiance when the sun scan over the field of view of the absolute radiometers to simulate the onboard state. And we have operated the measurement with the prototype of STIM. The SIAR-1 is traceable to WRR and serves as a transfer standard. So simultaneous comparison measurements between SIAR-1 and each of the three wide view absolute radiometers are measured to provide calibration corrections to the instrument. And we have a further study at the influence of stray light to the measurement results. This paper presents the method of simulation experiment and calibration for solar irradiance measurement with Solar Total Irradiance Monitor on board.
The conical black cavities are used in the Solar Irradiance Absolute Radiometers (SIARs) of the solar constant monitor aboard on the SZ spaceship and of the Solar Total Irradiance Monitor (STIM) aboard on sun-synchronous polar orbit weather satellites. A low reflectance measurement instrument which is used for making the integrating measurement on the reflectance of the conical black cavity in a high precision within the full hemisphere (include the entrance of the Ulbrichtsphere) has been constructed. The characteristic of the instrument is the employment of a semi-transparent mirror, which is mounted in an inclination angle of 45 degrees in front of the entrance of the Ulbrichtsphere. The incident beam is reflected to the black cavity or white board by the semi-transparent mirror. A portion of those, which is made diffused reflection through the black cavity or white board, is measured by the detector located in the side face of the Ulbrichtsphere, and the other portion which is reflected to the entrance is measured by the other detector, after passing through the semi-transparent mirror, and then being focused on by an ellipsoidal mirror. The two measurement data are added up to get the integrating reflectance within full hemisphere. The presentation and verification on the measurement result of the reflectance of the black cavity and its precision are described in this article. The absolute accuracy can reach 0.012%.
n order to studying long-term climate variability and globe environment change, Solar Total Irradiance Monitor (STIM) is constructed planed to aboard on FY-3 sun-synchronous polar orbit weather satellites. STIM is made up of three same absolute radiometers, which are similar with Solar Irradiance Absolute Radiometers (SIAR). We designate one radiometer as revising radiometer. It works only one day once one or two months to demarcate the drift of the other two radiometers. Solar irradiance is measured when the sun scans over the field of view of the absolute radiometers, respectively. The irradiance measurement is carried on at the position near the North Polar after the satellite move out the shade of the earth. SIAR is electro-calibrated cavity absolute radiometer. SIAR-1 had completed The Ninth International Pyrheliometer Comparisons (IPC-IX) with World Radiometric Reference (WRR) in Physikalisch-Meteorologisches Observatorium Davos /World Radiation Center (PMOD/WRC), Switzerland from 25 September to 13 October 2000, the comparison results showed that SIAR-1 is 0.078% higher than WRR. So SIAR-1 was given a WRR calibration factor 0.99922. Where after, we compared STIM with SIAR-1, and draw a conclusion: that the absolute accuracy of STIM is better than 0.2%.
For usual solar total irradiance monitor, the absolute radiometer is mounted on a sun auto tracking system. This paper introduces a new method of measuring solar total irradiance on Heliosynchronous Polar-Orbit Satellite. The solar total irradiance monitor is made up of the three same absolute radiometers with ±7.5° field-of-view which are mounted onto one section plane. Because the angle between the orbit plane and solar meridian plane is stationary for sun-synchronous polar-orbit satellite, the three radiometers are mounted on the plane which is parallel to the solar meridian plane. When the satellite runs in orbit, measurement will be taken at the overhead time when the sunscans over the three radiometers' field of view respectively. The three absolute radiometers are cavity electrically-calibrated absolute radiometers with measurements precision and uncertainty of less than 0.05 percent and 0.2 percent, respectively. In our method, since the variation of primary aperture area with angel is different from that of tracking mode, we use a simplified model in which the area variation with angle is expressed by cosine function. Formulae and curves obtained by differential equation of thermodynamics of the simplified mode in non-tracking model are similar with that in the sun- tracking mode. The theoretical analysis and simulation calculation proved the precision by our method could reach the same level as that of the sun-tracking mode, but the construction of instrument is much simple.