Description of the payload

The NIGHTGLOW instrument consists of three telescopes (each has a 14" diameter mirror and a 19" focal length - an f/1.4 design) instrumented with two photomultiplier tubes (PMT). A PMT is a very sensitive device for converting light into an electronic signal.

A filter is used to limit the light entering the telescopes to wavelengths between 300 - 400 nm - in the (invisible) near ultra-violet part of the spectrum.

One of the three main telescopes looks down at all times, while the other two rotate and view the ground, the horizon and the UV glow at high altitudes (above the balloon at ~90 km).

Flying at an altitude of about 30 km (100,000 ft), NIGHTGLOW will circumnavigate the world. During the local night, NIGHTGLOW will use its three onboard telescopes to measure the amount of ultraviolet light produced in the atmosphere, as well as that produced by humans on the ground.

In addition, NIGHTGLOW has two cloud sensing systems onboard to monitor the amount of cloud cover beneath the balloon. One system measures the cloud's temperatures with an infrared camera, and the other system measures the cloud's reflecting properties with a blue laser.

Combining the knowledge of the cloud cover and the light production, NIGHTGLOW will provide valuable data for scientists who are interested in measuring the very highest energy cosmic rays, particles of immense energy that come to us from outside our own Milky Way galaxy. These particles strike our atmosphere and create flashes of invisible ultraviolet light. NIGHTGLOW will help in the identification of these particle flashes, distinguishing them from the background ultraviolet light.

:: The balloon ::

The Ultra Long Duration Balloon (ULDB), is a project to develope a balloon system capable of providing scientific measurements for 100-day missions with floating altitude close to 35km.

It is a super-pressure balloon made of a composite fabric (polyester + polyethylene film and fabric) that is filled with Helium and hermetically sealed. Meridional tendons provide additional rigidity to the envelop. The pressure inside the envelop is maintained above the ambient pressure at all times to keep the balloon afloat at a constant altitude. During daytime the internal pressure increases due to solar heating but the volume remains constant due to the rigidity of the envelop. At night the pressure drops due to infrared radiative cooling to space, but as long as the internal pressure remains above the ambient pressure, the balloon stays at the same altitude.

Transported by stratospheric winds around the globe at 30m/s can circumvent the Earth in about 2 weeks. The balloons are 120 meters in diameter and can carry payloads up to 1500kg.

Details of the balloon flight and scientific outcome

 

Launch site: Australian Balloon Launching Station, Alice Springs, Australia  
Balloon launched by: National Scientific Balloon Facility (NSBF)
Balloon manufacturer/size/composition: Ultra Long Duration Balloon 800.000 m3 - SF4-18.38-1.5/.8-N
Balloon serial number: R18.38-1.5UI-02
Flight identification number: 495NT
Payload weight: 2485 lbs
Gondola weight: 2015 lbs

The balloon was launched at 9:21 a.m. local time on Febraury 25th, 2001 by dynamic method assisted by a crane as launch vehicle and using a auxiliary balloon to help to deploy the Ultra Long Duration Balloon material.

The initial ascent phase was very close to predicted ascent, but the balloon failed to pressurize.

The maximum altitude attained was of ~26 km (~85,000 ft) so the balloon was terminated.

The payload was recovered, but there was not enough time left in the campaign to repair it and get ready for a second launch, given the late date of the first attempt.

After examination apparently the release of collar at launch tore a hole in the balloon shell under the cap, hence the leak experienced.

The flight campaign of January/February 2001 was hampered by unusually heavy rains in Alice Springs including a local flooding of the Todd River, which flows through downtown of the city.

There were two launches of the ultra-long-duration balloon. The first carried the NIGHTGLOW payload. This flight was aborted due to abnormal balloon performance at an altitude of approximately 80,000 feet. The flight only lasted a few hours and no science data was returned.

The payload was recovered, but there was not enough time left in the campaign to repair it and get ready for a second launch, given the late date of the first attempt.

The NIGHTGLOW payload was packed up and shipped back to the United States for refurbishment.

External references and bibliographical sources

Images of the mission

NIGHTGLOW gondola detail. ULDB balloon a few minutes before the launch.