Accession Number : ADA315578

Title :   Improvement of Real Time f0F2 Prediction for OTH Radars.

Descriptive Note : Interim rept.,

Corporate Author : PHILLIPS LAB HANSCOM AFB MA

Personal Author(s) : Dandekar, B. S.

PDF Url : ADA315578

Report Date : 29 AUG 1995

Pagination or Media Count : 52

Abstract : Dandekar and Buchau (1986) presented an empirical algorithm for improving the f(0)F(2) predictions for the sunrise transition period. The algorithm uses an average hourly gradient obtained from the previous four days f(0)F(2) observations and the 'present' f(0)F(2), to predict f(0)F(2) for the next hour. A further improvement was achieved by adding a second order correction term to the averaged slope. The second order correction takes into account (1) the change in 'now' f(0)F(2) with respect to the previous four days' average f(0)F(2) and (2) the increasing/decreasing gradient of f(0)F(2). In the algorithm the sign of the second order term is selected so as to set a converging trend for the correction term. The algorithm is applied to a 24-hour period by dividing the time interval in two sections (04-16 and 16-04 LT) and reversing the sign of the second order correction for these two intervals, to assure the use of the converging trend from the algorithm for the 24 hour cycle. The scheme reduces the standard error in prediction from 0.9 MHz using the lONCAP method to 0.4 MHz at high solar activity and from 0.5 MHz using IONCAP to 0.9 MHz at low solar activity. The algorithm proposed here improves the f(0)F(2) prediction by 50% at high solar activity and by 40% at low solar activity. The method provides a minimum of 25% improvement in the real time prediction of f(0)F(2) for 80% of the time. This level of reduction in the error of prediction of f(0)F(2) is useful to the OTH radar frequency management, becuse every 6% change in 'M' (ratio of radar frequency to f(0)F(2) at midpoint of the radar range) requires an adjustment of the radar operation frequency.

Descriptors :   *PREDICTIONS, *REAL TIME, *OVER THE HORIZON RADAR, ALGORITHMS, FREQUENCY, TIME INTERVALS, RATIOS, REDUCTION, RADAR EQUIPMENT, TRANSITIONS, RANGE(DISTANCE), SOLAR ACTIVITY, CORRECTIONS, INTERVALS, SUNRISE.

Subject Categories : Computer Programming and Software
      Active & Passive Radar Detection & Equipment

Distribution Statement : APPROVED FOR PUBLIC RELEASE