NISAR, an acronym for NASA-ISRO Synthetic Aperture Radar, the ambitious collaborative project between NASA and ISRO, is expected to be a milestone in the innovation of next generation satellites and open up a new chapter in Indo-US space partnership.
The unique project, touted as the most expensive satellite so far, is set for launch around December 2020 and will spearhead a number of technological changes, ushering in a new age of earth monitoring satellites with unprecedentedly powerful resolution, said Dr Paul A Rosen, a senior scientist at NASAL Jet Propulsion Laboratory and Caltech.
Dr Rosen, who is involved in the project, was speaking at the at the 38th ACRS (Asian Conference on Remote Sensing) being held in New Delhi from October 23 to 26.
Two outstanding firsts in the world
What makes the NISAR project more gargantuan in scale and scope and breathtaking in vision and ambition, is the amount of money that both the space organizations will invest in it – whopping $1.5 billion — making it the world’s most expensive satellite manufactured so far.
NISAR will also be the world’s first dual frequency radar imaging satellite. It will be used to monitor and observe a wide range of natural phenomenon from outer space and would have many applications, spreading over multiple fields and domains.
NISAR will have two frequency bands — L and S. The L band is for low temporal decorrelation and foliage penetration while the S band is for sensitivity to lighter vegetation. The former is being developed by NASA and ISRO is working on the latter.
“What we are doing is looking at time variability of the Earth over the life of the mission to understand how disasters evolve, how earthquakes occur, how volcanoes occur, how the ice sheets are changing and affecting sea level rise, and how forest fires and changes in the forest cover affect the atmosphere,” added Dr Rosen.
NISAR will be launched aboard a GSLV Mark-2 rocket that would be provided by ISRO. The satellite would send detailed sampling report in every 12 days.
NISAR focus and objectives
NISAR will mainly focus on global coverage, vector measurements and dense sampling in time. It will monitor and analyze global dynamics of ice sheets and sea ice, wetlands and arable land and the change in biomass.
It will also help in disaster prediction and a swift response to it, infrastructure monitoring, and forestry and agricultural applications.
NISAR will be valuable in understanding the response of ice sheets and interaction of sea ice and climate; understanding the complex dynamics of carbon storage and arid, wastelands, arable, forest covers and permafrost system.
In order to meet global food security targets, agricultural monitoring by NISAR would be of great help, and more light would be shed on societal ramifications of isolated carbon dioxide reserves and hydrocarbons
What is SAR and its utility?
SAR (Synthetic Aperture Radar) is an airborne radar system that is used to get high resolution 2D/3D images of various landscapes. Striking characteristic of SAR is that it is independent of altitude and weather and wind fluctuations, making it the most preferred satellite technology in topography, oceanography, glaciology, geology and earthquake and volcano monitoring.
A SAR image is created by transmitting successive pulses of radio waves to illuminate a target scene, and recording the echo of each pulse. The pulses are transmitted and the echoes received using a single beam-forming antenna
As the SAR device mounted on a satellite moves, the antenna location relative to the target changes with time.
Signal processing of the successive recorded radar echoes allows the combining of the recordings from these multiple antenna positions. This process forms the synthetic antenna aperture and allows the creation of higher-resolution images that would be an impossibility using physical radar antennae.
In the present times, SAR systems are the need of the hour and the only way for high resolution images.
Now imagine what would be the quality of images when two SAR’s are combined and synchronized?
NISAR certainly has the potential to revolutionize a lot of industries by its never-before released ultra-high resolution satellite imagery. The technology used in NISAR would be an enabling technology, providing impetus for more research and development and the technical details of all its constituent bands would be made available in open source.