  High altitude scientific balloons offer unique opportunities to carry
scientific payloads to stratospheric altitudes at a cost several orders of
magnitude lower than corresponding satellite missions. Balloon-borne payloads
are easy to implement allowing quick experiment turn-around times and
inexpensive reflights can be conducted as payload is most of the times
recovered. In addition, in-situ and high resolution spatial and temporal
measurements of the earth's atmosphere can be made that might not be feasible
with satellites. It is also used as a testbed to prove technologies for future
satellite missions. Scientific ballooning was initiated at the Tata Institute
of Fundamental Research (TIFR) in the year 1945 when scientific instruments
were flown to stratospheric altitudes using a cluster of weather balloons for
cosmic ray research. The need to have balloons float at constant stratospheric
altitudes for astronomy studies led to the initiation of work on design and
fabrication of Zero-Pressure polyethylene (ZP) balloons at TIFR in 1956. Since
then several ZP balloon flights were conducted for studies in astronomy,
atmospheric science, astrobiology, balloon technology and space technology
development, leading to several important scientific results. In the year 2018,
TIFR balloon program crossed an important milestone of conducting more than 500
ZP balloon flights. This paper presents recent advancements made in some areas
of scientific ballooning and the details of balloon experiments conducted in
the past two decades.
