Mission Summary
20020903I Aircraft 43RF
Two plane CBLAST mission into Tropical Storm Edouard

Scientific Crew (43RF)

Lead Scientist	P. Black
AXBT Scientist	E. Uhlhorn
Radar scientist	M. Black
GPS Dropsonde	M. Black
HRD Workstation	M. Black
FRD BAT probe	S. White
SRA	Ed Walsh (NASA)
PMS/CIP probes	not installed not operating
Scripps laser alt.	not operating

Mission Briefing:

This mission was designed to test the hurricane planetary boundary layer (PBL) flight pattern in weak tropical storm conditions, to flight test new CBLAST instrumentation in wind and rain and to execute BAT probe calibration maneuvers. A two-plane CBLAST/Ocean Winds research mission in TS Edouard was scheduled for September 3, 2002, departing MacDill AFB at 1 PM EDT and recovering at MacDill approximately 6.5 hours later.

N42RF and N43RF will fly coordinated, stacked figure-4 patterns at 3,000 and 5,000 feet, or alternately at 5,000 and 7,000 feet. N42RF will then execute two step-descent patterns, while N43RF flies overhead.

Mission Synopsis

Detailed mission briefings were held with AOC flight directors and navigators one hour before the flight brief to discuss any problems with the flight segments being planned. A detailed briefing was then held two hours prior to the mission to discuss the CBLAST mission profile with lead mission scientists, flight directors, pilots, navigators, flight engineers and SED chief electronics engineers.

NOAA43 departed MacDill on time at 1707 GMT followed 20 minutes later by NOAA42. NOAA42 returned to MacDill at 2330 followed one hour later by NOAA43, durations of 6 hr, 15 min and 7 hr, 30 min, respectively. Three AXBTs were deployed from NOAA43 and one GPS dropsonde in the figure 4 pattern as well as 4 GPS sondes in the eyewall/rainband. NOAA42 deployed 8 GPS drops in the eyewall/rainband as well as 4 GPS/AXBT combo drops in the figure 4 pattern.

NOAA43 flew the BAT probe calibration maneuvers at 1,000 ft near NDBC buoy 41012 enroute to the IP while waiting for NOAA42 to catch up, i.e. clockwise and counterclockwise circles at 30° bank followed by a wind box with two minute legs. NOAA42 then arrived and the aircraft linked patterns with NOAA42 trailing NOAA43 by 2-4 nm, or about 30-60 seconds flight time. Flight altitudes were 7,000 ft for NOAA42 and 1,000 ft for NOAA43, except for 5,000 ft during the rainband/eyewall segment penetration during the 'figure 4' portion of the flight. The leg lengths of the figure 4 pattern were 60 nm.

The intense convective band on the east side of the storm was penetrated by both aircraft. Peak reflectivities were 45 dBZ. Peak penetrated reflectivities were 35-40 dBZ. Band thickness was about 30 nm resulting in about 7 minutes duration in the band.

The deployment of 12 sondes in rapid succession was executed by the two aircraft with NOAA42 initiating their 8 sonde deployment sequence just prior to entering the convection. Due to depressurization for free fall launching of AXBTs, insufficient differential pressure was available for GPS sonde deployment and the first sonde stuck in the tube. Subsequent sondes were hand launched out the AXBT free-fall chute. About 30 seconds later, NOAA43 began its sequence of 4 GPS sonde deployments from 5,000 ft with 10-20 seconds between drops. The problem on NOAA42 resulted mainly from HRD personnel delivering AXBTs planeside late prior to take-off which resulted in external tube loading difficulties. This necessitated loading of AXBT's inside of the aircraft and a subsequent free-fall launching method.

Following completion of the figure 4 on the south side of the storm, NOAA43 then began the first of two boundary layer stepped descent patterns while NOAA42 flew across convective bands in between stepped descents. The two aircraft flew 5-6 min legs radially outbound and then inbound from the two initial points 40 nm southeast of the center and 40 nm northwest of the center at an indicated airspeed of 220 kt (penetration airspeed). NOAA43 flew at 600 ft while NOAA43 flew at 7,000 ft.

Following the cross wind pattern, NOAA43 climbed to 3500 ft and began the along wind flight legs, downwind for 5 minutes, upwind for 6 minutes. Weather in the southeast was shallow towering cumulus with some light rain showers. Surface winds were about 30 kt. Upwind downwind legs were then flown at 2,000, 1,000, 600, 400 and 200 ft during the along wind portion of the PBL pattern. NOAA43 then proceeded through the center to execute a similar cross wind and stepped descent sequence on the northwest side of the storm in surface winds of about 30 kt. Turbulence levels felt somewhat stronger on the NW compared to the SE.

The coordinated pattern was flown nearly flawlessly by AOC crew. The only problem was too many airspeed changes by both aircraft in an effort to maintain precise lateral aircraft separation. This resulted in frequent aircraft pitch changes with affected tail Doppler radar and IWRAP data.

Problems:

A major problem was encountered with the BAT probe on this flight. The short period of rainfall caused extensive damage to the probe spherical head, pulverizing the paint, outer gel coat and inner composite material. The probe was removed from the aircraft after the flight and shipped to FRD for repair and redesign.

The SFMR on NOAA43 experienced significant radio frequency interference (RFI) at the altitudes below 5,000 ft. Terry Lynch was able to diagnose the source of this contamination as coming from the TA X-band radar on NOAA43, which contaminated the 6.02 and 7.20 GHz frequencies and the C-band altimeter, which contaminated the 5.06 GHz frequency. It was found that the onboard processing software did not have the software installed to eliminate contaminated frequencies. The needed software is being installed by Al Goldstein of AOC. Future flights should therefore be able to compute surface winds as usual using fewer frequencies from low flight altitudes despite the RFI. AOC engineers will investigate why filters previously installed on the C-band altimeter failed to prevent RFI and also why an X band tail radar is transmitting energy at the high end of the C-band frequency range.

A slight problem with the flight plan was experienced. The along wind, stepped descent part of the pattern tended to drift down stream with time, indicating that legs on the downwind segments were too long and too short on the upwind segments. Timing will have to be adjusted in the future, especially at higher winds. Downwind legs will need to be shortened and upwind legs lengthened. Also, a heading change may be required at leg midpoints to keep the aircraft track aligned with the changing wind direction. Along wind legs should be flown at close to zero drift angle.

Peter Black
Lead Scientist

Mission Data

Return to Mission page.