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Using sea surface temperature (SST) and wind speed retrieved by the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), for the period of 1998-2003, we have studied the annual cycle of SST and confirmed the bimodal distribution of SST over the north Indian Ocean. Detailed analysis of SST revealed that the summer monsoon cooling (winter cooling) over the eastern Arabian Sea (Bay of Bengal) is more prominent than winter cooling (summer monsoon cooling). A sudden drop in surface short wave radiation by 57 W m -2 (74 W m -2 ) and rise in kinetic energy per unit mass by 24 J kg -1 (26 J kg -1 ) over the eastern Arabian Sea (Bay of Bengal) is observed in summer monsoon cooling period. The subsurface profiles of temperature and density for the spring warming and summer monsoon cooling phases are studied using the Arabian Sea Monsoon Experiment (ARMEX) data. These data indicate a shallow mixed layer during the spring warming and a deeper mixed layer during the summer monsoon cooling. Deepening of the mixed layer by 30 to 40 m with corresponding cooling of 2 C is found from warming to summer monsoon cooling in the eastern Arabian Sea. The depth of the 28 C isotherm in the eastern Arabian Sea during the spring warming is 80 m and during summer monsoon cooling it is about 60 m, while over the Bay of Bengal the 28 C isotherm is very shallow (35 m), even during the summer monsoon cooling. The time series of the isothermal layer depth and mixed layer depth during the warming phase revealed that the formation of the barrier layer in the spring warming phase and the absence of such layers during the summer cooling over the Arabian Sea. However, the barrier layer does exist over the Bay of Bengal with significant magnitude (20-25 m). The drop in the heat content with in first 50 m of the ocean from warming to the cooling phase is about 2.15 · 10 8 J m -2 over the Arabian Sea.

This article discusses the developmental challenges of the low-thrust, long-duration solid rocket motor for the launch of the experimental Reusable Launch Vehicle-Technological Demonstrator (RLV-TD). The main challenges were: (1) developing a motor case and subsystems with low inert mass; (2) design of an optimum nozzle such that the motor can have maximum specific impulse at atmospheric conditions, but with no flow separation at low operation pressures; (3) developing a slow-burning propellant (3 mm/s) to meet the mission requirements; (4) design of propellant grain for the motor so that it has long burning time, the vehicle experiences low dynamic pressure at the transonic regime, and the motor is without combustion instability; (5) developing necessary thermal protection system to take care of long-duration operations, and (6) developing the igniter to ensure the ignition of the motor, especially when easy ignition is difficult with slow-burning propellants and that there should be sufficient overlap of igniter functioning with motor initiation. Performance of the motor in flight indicated that the design met all the required criteria within the expected tolerance.

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