After more than a decade of development, NASA's science leadership traveled to India this week for the launch of the world's most expensive Earth-observation satellite.
The mission, a $1.5 billion synthetic aperture radar (SAR) satellite, a joint project between NASA and the Indian space agency ISRO, successfully launched into orbit on Wednesday aboard India's GSLV or Geosynchronous Satellite Launch Vehicle, a medium-lift rocket.
The mission, named NISAR (NASA-ISRO Synthetic Aperture Radar), was subsequently deployed into its intended orbit 464 miles (747 km) above the Earth's surface. From this Sun-synchronous orbit, it will collect data about the planet's land and ice surfaces two times every 12 days, including the infrequently visited polar regions in the Southern Hemisphere.
The description of the SAR is that it's dual band, S-band and L-band. Those frequency bands are adjacent to each other and not at all completely dedicated to SAR use. L-band is broadly defined as 1 to 2 GHz (1000 to 2000 MHz) while S-band is equally broadly defined as 2 to 4 GHz (2000 to 4000 MHz). For example, L-band contains satellite downlinks, aviation services such as TCAS (Traffic Collision Avoidance System), transponder, ADS-B and GPS, while S-band includes the 2.4 GHz WiFi we're so dependent on, Bluetooth, microwave ovens, and many consumer radio controlled devices.
Broadly, telling us the radar is dual band, using S-band and L-band, is telling us only the tiniest amount of information.
The satellite combines two main instruments that, unlike optical telescopes, can gather data through clouds and at night. NASA provided the L-band synthetic aperture radar, which is efficient at measuring soil moisture, forests, and the movement of land and ice on the surface of the planet. India contributed an S-band radar that is useful for measuring agricultural changes, as well as grasslands and human-built structures.
NASA and other spaceflight organizations have been developing and flying synthetic aperture radar for decades, but the NISAR spacecraft is one of the first missions to combine two different bands onto a single vehicle. This should provide a more comprehensive view of how the planet's surface is changing on a real-time basis.
The NISAR spacecraft - in the middle - is integrated with its Indian GSLV launch vehicle. Image Credit: ISRO
As is usually the case, the satellite will spend a while getting calibrated and more thoroughly tested, once it's in the preferred orbit. That process of getting readied for its mission is expected to take three months.
During this time NISAR will deploy a very large antenna reflector that is 39 feet (12 meters) in diameter. This reflector will send and receive microwaves from the two radars and use differences to measure the surface below.
The mission is notable for both its complexity and its cost (those usually come together, after all).
The US and Indian space agencies signed the partnership agreement on September 30, 2014, to design and build the spacecraft. At the time, launch was targeted for 2024, so missing that deadline by less than a year is quite respectable.
Very interesting. Agreement signed in 2014 when Falcon 9 was already on line and saving everyone serious money with reduced launch costs.
ReplyDeleteOne of the first space SAR missions was STS-99 - The Shuttle Radar Topography Mission (SRTM).
ReplyDeleteWhat did I miss? Is the sat made by Americans, or is it of Indian origin? Or a collaboration of both? Was it launched on an Indian rocket because we didn't have any heavy lift available or hardware that would work?
ReplyDeleteInquiring idiots would like to know!
Nasa made the L band, India made the S band. From Wikipedia : "ISRO's share of the project cost is about ₹788 crore (US$93 million), and NASA's share is about US$1,118 million." Citation listed some source docs; I did not read deeper. Unknown if the launch cost was included in the above, if that is the discrepancy in total costs. Unknown if the Nasa made direct payments to India or the L band cost the $1.1 billion.
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