April 13, 1996

Mission Summary

DC-8 SUCCESS flight #202 (scientist: Brian Toon)

SUMMARY: The basic flight went very well. All of the instruments are functioning, with some small problems left to be worked out. We met all of our major objectives, testing instruments, calibrating the MMS and transiting to Kansas. We also met most of our secondary objectives. We were able to sample our own contrail and cirrus for a significant period of time. However, the rendezvous with the T-38 did not work out due to logistical problems, and contrails were not present at the time it was attempted. Several preliminary science observations were made that are interesting, including size of ice crystals in cirrus and contrails, IWC of contrails, and possible compositional clues about ice nuclei.

Mission Objective

DC-8 TEST-FLIGHT

• a second test for the instruments
• to calibrate the MMS system with the canards on the aircraft
• to transit to Kansas

• to investigate cirrus and contrails as found
• to sample stratospheric air for part of the flight
• to follow the NASA T-38 flown by Marty Knudsen to practice flying in exhaust.

Flight Log

OPERATIONS
FLIGHT PLAN:
Planned takeoff: 17.00 GMT (10.00 local time)
PART 1: Off California Coast. The plan here is to repeat the general pattern of the previous flight of 4/10/96 in a restricted space over the water. We will first do low altitude (5kft) boxes to calibrate the MMS. We will then ascend to about 20kft and again perform box manuevers. Finally, we will ascend to just below the tropopause and again perform box manuevers. The trop height will be identified from MMS in advance of the final altitude change. We will perform several 30o banking turns at max. altitude in an attempt to encounter our own exhaust/contrail. The lidar will be operated in a forward scanning mode during all of this period. Turns should be made to the right so that the lidar can see the contrail ahead of the aircraft. This portion of the flight will require about 2 hours.
PART 2: Transit across California and Nevada. There is some chance of encountering cirrus on this leg. Therefore we would like to stay just below the trop as measured by MMS, or descend if needed into cirrus. Laser in vertical mode.
PART 3: Transit across eastern Nevada and Utah. We expect no cirrus in this region. We would therefore like to cross into the stratosphere once we cross the jet. We will have to identify the location of the jet crossing in real time therefore, we will request max altitude possible on this leg. Laser off when we enter Denver airspace.
PART 4: Once we enter New Mexico it will again be possible to find cirrus. We would like to descend below the trop (from MMS) and locate an altitude where the DC-8 is making a good contrail.
PART 5: We will rendezvous with the T-38 over New Mexico and Kansas. Our emphasis is on in-situ observations of the exhaust rather than lidar. We will try to sample the exhaust or contrail of the T-38. It is not possible to fire the laser in a forward mode so we will use it in a vertical mode. If we cannot see the exhaust visually, we will use Weinheimer's instrument to try to identify when we are in the exhaust. We would like to stay in the exhaust for 3-4 min, then stay out of it for an equal period of time.
PART 6 Land in Kansas.

TAKEOFF/LANDING
The DC-8 left Ames at 17.15 UTC (10.15 am local time) and arrived at Salina at 22.30 UTC

FLIGHT REPORT
Take off was 17.14:34 GMT. Power up procedures are starting too late, and MMS still has problems maintaining the INS calibration during the power up sequence.
PART 1: The calibration manuevers for the MMS were successful at all altitudes. However, the pilots were not able to perform the Yaw manuevers at the highest altitude. At least 3 people were airsick from these manuevers. We also encountered cirrus over the ocean so we were able to test the ice instruments. The cirrus seemed to have relatively small particle sizes, so much of it may have been from old contrails. The pilots were able to do a thirty degree banking turn and stay within the contrail for much of each turn. The aircraft and the contrails cast a circular shadow on the ocean surface. Visually it was difficult to see the contrails ahead of the aircraft against the background of the pre-exisiting cirrus. However, it was clearly visible blowing over the cockpit of the DC-8.
PART 2: cirrus were present along this part of the flight. We crossed into the stratosphere near the Utah border. The DC-8 continued to lay a contrail even though we were a thousand feet above the trop.
PART 3: We were in the stratosphere here as desired.
PART 4: No cirrus were present along this leg, and the DC-8 did not lay a contrail. Even at 35kft the in situ sensors suggest that we are still in the stratosphere.
PART 5: We do not expect to see the T-38 contrail. Therefore, we are using the Weinheimer instruments and CN counters to look for the exhaust trail. The T-38 was easily visible from the DC-8 as it moved in front of us. However, given the airspeed difference, short flight time of the T-38, and problems in setting up the rendezvous not enough time was available to complete this exhaust manuever.

METEOROLOGY-REPORT
FORECAST: There are several rapidly moving systems crossing the US that may be encountered. In the region just off the California coast there may be cirrus near the tropopause, however cirrus is expected to build during the day, so we might be too early for it. Cirrus is also expected over Western Nevada. We should pass into the stratosphere over Eastern Navada and Utah as we cross a jet stream. No cirrus are expected in this region. Cirrus or contrails may also be present between New Mexico and Kansas. However, the cirrus are moving away as the day progresses so we might miss them.
OBSERVATIONS: There were cirrus and contrails present throughout the altitude range 25-39kft over the Pacific ocean. Numereous persistent contrails were present so it was often difficult to distinguish visually the contrails from cirrus. At 35kft where we did the final manuever for the MMS we had cirrus At take off broken fair weather cumulus were present with scattered cirrus over Ames. Local cirrus were not predicted earlier. Cirrus were not present over Oregon, or Northern California. The trop was also significantly lower than expected, so part of the flight to the north was in the stratosphere. We requested a descent into a low cloud deck, probably around 20kft on the south bound leg toward the restricted area.

INSTRUMENT STATUS
All of the instruments on the DC-8 are functional for this flight. The wing tip instruments are a replicator (Hallet), VIPS, MASP and 1-DC. When in cirrus the CVI would like altitude changes at 1000 ft/min or less.

• BALLENTHIN: good shape, but mass spec is picking up odd peak when heater turned up.
• BAUMGARDNER: Over heated in low level flights, then worked fine. Need to pull probe for calibration.
• BRUNE: Much improved. Still had problems moving center body. Needs to install a new inlet on Sunday.
• CHAN: Worked 95%. (missing two high frequency temperature sensors). Calibration successful.
• COGGIOLA: Working well. Software still to work on. Some repairs made in flight.
• COOPER: CCN had some lines freezing up so it was only run to -20C. CN worked fine, but did not show any enhancement in contrail interceptions.
• DADS: Worked fine. But three stage humidty sensor failed.
• FERRY: Impactors and data system worked fine.
• GARY: Instrument worked fine.
• GERBER: Worked just fine.
• HAGEN: Some minor leaks, but basically worked well.
• HALLET: replicator worked well, but there are some air flow problems in the PMS pod..
• HEYMSFIELD: Almost everything worked ok. 1-D probe is not working. Saw high concentrations of small particles in contrail.
• HUDSON: Worked well. Temperature control problem for 30 min. Pump not working well at high altitude. Saw CCN up by a factor of two in contrail.
• LAWSON: Problems with probe false triggering so it was ineffective imaging ice crystals.
• RODGERS: Ice growth at -15C affected ice nucleus counter. CN counter worked fine.
• SACHSE: Dacom and water worked well, but high cabin temperature caused some drift.
• TALBOT: No problems.
• TWOHY: Reported that much of the cirrus over the Pacific seemed to contain involatile aerosols. There were about 2x10^3 of these per liter which is a high ice crystal concentration, assuming that each aerosol corresponded to one ice crystal. IWC in contrail similar to surrounding cirrus, the contrail had about 4 times as many particles. Everything working well.
• UTHE: Lidar worked fine. Still working on software.
• VALERO: Everything fine, but have one channel out on upward looking TDDR.
• WEINHEIMER: Worked fine. Saw NOy on cirrus, and in DC-8 contrail. Needs more time at constant altitude.

Mission Highlights

• The nuclei inside the ice crystals sampled over the ocean were not volatile (Twohy). This is a surprising result. Many of these cirrus may have been contrails.
• The particle sizes in these clouds were surprinsingly small (Hallett, Twohy, Heymsfield), which is again consistent with old contrails.
• NOy was seen on ice particles.