BIRD (Balloon borne Investigations of Regional atmospheric Dynamics)

BIRD was the acronym for Balloon-borne Investigations of Regional-atmospheric Dynamics an experiment designed to study wave dynamics in the mesosphere and lower thermosphere (MLT) region using daytime optical measurements. The experiment investigated atmospheric wave structures at low and equatorial latitudes through measurements of airglow emissions at different wavelengths. The ultraviolet measurements targeted MgII emission at 280.0 nm, originating at approximately 85~110 km, and OI emission at 297.2 nm, originating at approximately 110~130 km. The measurements were intended to determine the horizontal scale sizes and temporal characteristics of waves in these altitude regions.

BIRD was a joint Indo-US experiment involving the Space and Atmospheric Sciences Division of the Physical Research Laboratory (PRL), Ahmedabad; the Center for Space Physics at Boston University; the Center for Atmospheric Research at the University of Massachusetts Lowell; the Space Telescope Science Institute; and the Space Physics Laboratory at the Vikram Sarabhai Space Center (VSSC), Trivandrum.

The instrumentation was installed on a gondola developed at the National Balloon Facility of the Tata Institute of Fundamental Research (TIFR) which can be seen in the image at left.

The main ultraviolet instrument was the Ultraviolet Imaging Spectrograph (UVIS). It was designed to provide an 80° field of view with a spectral resolution of approximately 0.2 nm at 297.2 nm. The optical system used reflecting elements, with an ultraviolet filter and a fused-silica Schmidt corrector plate as the only thin transmissive elements. The input optics consisted of a convex spherical primary mirror with a radius of curvature of 2 cm and a concave spherical secondary mirror with a focal length of 60 cm and a diameter of 15 cm. Radiation entering the instrument was focused onto a slit measuring 45 × 0.5 mm.

An ultraviolet filter was located immediately behind the slit. It had a transmission greater than 85% at 330 nm and a full-width-at-half-maximum bandwidth of 110 nm. It restricted the transmitted wavelength range to 275–385 nm. Transmission was greater than 60% at 280 nm and 70% at 297.2 nm. The filtered radiation was directed to an off-axis parabolic CollimatorCollimatorA collimator is a device which narrows a beam of particles or waves, either to cause the directions of motion to become more aligned in a specific direction or to cause the spatial cross section of the beam to become smaller. In optics, a collimator may consist of a curved mirror or lens with some type of light source and/or an image at its focus. This can be used to replicate a target focused at infinity with little or no parallax. In X-ray optics, gamma ray optics, and neutron optics, a collimator is a device that filters a stream of rays so that only those traveling parallel to a specified direction are allowed through. mirror with a focal length of 60 cm and a diameter of 13 cm. The CollimatedCollimatorA collimator is a device which narrows a beam of particles or waves, either to cause the directions of motion to become more aligned in a specific direction or to cause the spatial cross section of the beam to become smaller. In optics, a collimator may consist of a curved mirror or lens with some type of light source and/or an image at its focus. This can be used to replicate a target focused at infinity with little or no parallax. In X-ray optics, gamma ray optics, and neutron optics, a collimator is a device that filters a stream of rays so that only those traveling parallel to a specified direction are allowed through. beam illuminated a plane reflection grating measuring 120 × 100 mm with 1200 lines per millimeter.

The diffracted radiation was focused by a Schmidt camera with a focal length of 13.9 cm and a diameter of 100 mm onto a CCD detector. The detector had 1,000 × 1,000 pixels with a pixel size of 13 ?m and an enhanced ultraviolet coating. Its quantum efficiency was greater than 55% in the 260–800 nm ultraviolet-visible range. The reflecting optical surfaces were coated with ultraviolet-enhanced aluminum. UVIS had a dispersion of 0.07 nm per pixel and a spectral resolution of 0.21 nm at 297.2 nm.

The second optical instrument was the High Throughput Imaging Echelle Spectrograph (HiTIES). It was used to measure OI airglow emissions at 557.7 and 630.0 nm. The instrument used a 98.76-lines-per-millimeter echelle grating and f/3.4 optics. Its spectral resolution was 0.29 nm at 589.3 nm.

The instrument package included a single-board embedded computer running a Unix operating system for data acquisition. The system was configured to save spectral images onboard and transmit data to the control station.

Balloon launched on: 3/8/2010 at 10:52 ist
Launch site: TIFR National Balloon Facility, Hyderabad, India  
Balloon launched by: National Balloon Facility, Tata Institute of Fundamental Research
Balloon manufacturer/size/composition: Zero Pressure Balloon Antrix - 109.755 m3
End of flight (L for landing time, W for last contact, otherwise termination time): 3/8/2010 at 18:25 ist
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 7 h 35 m
Landing site: 380 km W of Hyderabad, India
Payload weight: 335 kgs

The balloon was launched from the National Balloon Facility in Hyderabad, India at 10:27 IST (Indian Standard Time) on 8 March 2010. After a nominal ascent it reached a peak altitude of 35.28 km by about 12:30 IST. The altitude as shown in the map above was almost constant until around 18:00 IST when the gondola was separated from the balloon and the instrument package was retrieved later that night.

• Balloon launch records Tata Institute of Fundamental Research
• Daytime wave characteristics in the mesosphere lower thermosphere region: Results from the Balloon-borne Investigations of Regional-atmospheric Dynamics experiment Journal of Geophysical Research: Space Physics Volume 119, Issue 3, pages 2229–2242, March 2014