Yesterday evening, the
skies above Sriharikota witnessed a triumphant moment as the Indian Space
Research Organisation (ISRO) successfully launched the NASA-ISRO Synthetic
Aperture Radar (NISAR) satellite aboard the Geosynchronous Satellite Launch
Vehicle (GSLV) Mark II F16 rocket with a precision that placed the satellite
within 3 kilometers of its intended orbit—far surpassing the 20-kilometer margin.
This magnificent launch marked a significant milestone in the storied
partnership between ISRO and NASA, two space agencies representing the world’s
largest and oldest democracies.
The successful launch of the
GSLV Mark II rocket and the placement of NISAR satellite in its intended orbit,
not only restored ISRO’s reputation after recent setbacks with the
PSLV-C61/EOS-09 and NVS-02 missions but also reaffirmed the belief of ISRO
founders in harvesting the applications of space for the benefit of humankind,
more particularly Indians. It also strengthens the enduring collaboration between
India and US that traces its roots to the visionary efforts of Dr. Vikram
Sarabhai, Dr. Homi Bhabha, and their contemporaries in ISRO and NASA in the
1960s and 1970s. The NISAR mission, a $1.5 billion endeavor, is poised to
revolutionize Earth observation with its dual-frequency radar imaging, offering
unprecedented insights into natural processes and aiding global efforts in
disaster mitigation, climate monitoring, and sustainable development, which are
now of extreme importance to the global community. Over the next three months,
as NISAR transitions from deployment to full operational capability, it will
usher in a new era of space applications, echoing the transformative impact of
ISRO’s Satellite Instructional Television Experiment (SITE) program of 1975.
The Deployment Process of
NISAR: A Three-Month Journey to Full Functionality
The successful launch of
NISAR on July 30, 2025, marked the beginning of a meticulously planned
deployment and commissioning process, expected to span approximately 90 days.
This phase is critical to ensuring that the satellite, equipped with NASA’s
L-band and ISRO’s S-band Synthetic Aperture Radar (SAR) systems, becomes fully
operational and ready to deliver high-resolution, all-weather, day-and-night
data. The deployment process can be broken down into several sub-phases, each
designed to prepare the satellite for its ambitious scientific objectives.
Launch and Initial Orbit
Stabilization (Days 1–10)
Following its precise
injection into a 743-kilometer Sun-synchronous polar orbit, NISAR’s immediate
post-launch phase involves stabilizing the spacecraft and confirming its
health. Mission controllers from ISRO’s Telemetry Tracking and Command Network
in Bengaluru and NASA’s Jet Propulsion Laboratory (JPL) have already confirmed
full signal acquisition, indicating that the satellite is functioning as
expected. During this period, the satellite’s solar arrays are deployed to
power its systems, and initial checks are conducted on the spacecraft’s
mainframe elements, including its attitude control systems, thermal regulation,
and communication subsystems. These checks ensure that NISAR is correctly
oriented and stable in its dawn-to-dusk orbit, which allows it to maintain
consistent solar illumination for power generation.
Antenna Deployment (Days
10–20)
A critical milestone in
NISAR’s deployment is the unfurling of its 12-meter mesh reflector antenna, the
largest radar antenna ever deployed in space. Mounted on a 9-meter deployable
boom, this antenna is essential for the satellite’s dual-frequency SAR operations.
The deployment process, scheduled to begin around the 10th day post-launch, is
a complex, multi-stage operation that requires precise coordination to extend
the boom and unfurl the gold-plated mesh reflector, which resembles a giant
beach umbrella. This step is crucial for enabling NISAR’s SweepSAR technology,
which allows the satellite to image a 242-kilometer swath with 5–10-meter
resolution. Engineers at ISRO and NASA will monitor the deployment closely,
ensuring that the antenna is correctly positioned and structurally sound.
Commissioning and
Instrument Calibration (Days 20–90)
The commissioning phase,
spanning the first 90 days, is dedicated to preparing NISAR for its science
operations. This phase is divided into sub-phases, including initial
engineering checks, payload activation, and instrument calibration. The L-band
(24 cm wavelength) and S-band (9 cm wavelength) radar systems, provided by NASA
and ISRO respectively, will undergo rigorous testing to ensure they operate
harmoniously. Calibration will involve the use of ground-based corner
reflectors, such as those hosted by the National Centre of Geodesy at
IIT-Kanpur and IIT-Patna, to fine-tune the radar’s accuracy during the in-orbit
checkout phase. These reflectors help validate the satellite’s ability to
detect minute surface deformations as small as a centimeter. Additionally,
JPL’s engineering payload and instrument checkout will confirm the
functionality of the high-rate communication subsystem, GPS receivers,
solid-state recorder, and payload data subsystem. By the end of this phase,
expected around late October 2025, NISAR will be ready to commence its primary
science mission, systematically mapping Earth’s land and ice surfaces every 12
days.
The Legacy of ISRO-NASA
Collaboration: From SITE to NISAR
The NISAR mission is a
testament to the deep and enduring partnership between ISRO and NASA, a
collaboration that began in the 1960s under the leadership of Dr. Vikram
Sarabhai, the founding father of India’s space program, and Dr. Homi Bhabha, a
pioneer in India’s scientific community. Their vision for leveraging space
technology for societal benefit laid the groundwork for one of ISRO’s most
transformative initiatives: the Satellite Instructional Television Experiment
(SITE) of 1975. This program, executed under the leadership of Prof. Satish
Dhawan and with contributions from Dr. E.V. Chitnis, who recently celebrated
his 100th birthday, used NASA’s ATS-6 satellite to broadcast educational and
health programs to 2,400 villages across India. The SITE program, often hailed
as the “TV revolution,” brought knowledge on agriculture, health, and education
to remote communities, demonstrating the power of space technology to bridge
developmental gaps.
The NISAR mission builds
on this legacy of international cooperation and societal impact. Unlike SITE,
which relied on a borrowed satellite, NISAR is a true 50/50 partnership, with
NASA contributing the L-band radar, radar reflector antenna, and critical
subsystems, while ISRO provides the S-band radar, spacecraft bus, and launch
services via the GSLV-F16. This collaboration, forged across 13 time zones and
a decade of effort, showcases the technical and diplomatic synergy between two
spacefaring nations. The mission’s open-data policy, which will make NISAR’s
data publicly accessible within 1–2 days of observation and in near real-time
for disaster response, echoes the democratizing spirit of SITE, ensuring that
the benefits of advanced Earth observation reach developing nations and global
communities.
NISAR’s Global Impact:
Revolutionizing Disaster Mitigation and Beyond
Once fully operational in
late October 2025, NISAR will transform how the world monitors and responds to
natural processes and hazards. Its dual-frequency SAR, capable of penetrating
vegetation (L-band) and detecting surface changes (S-band), will provide
high-resolution, all-weather imagery, making it a game-changer in several
domains:
Disaster Management and
Mitigation
NISAR’s ability to detect
surface deformations as small as a centimeter will enable early warning systems
for natural disasters such as earthquakes, landslides, volcanic eruptions, and
tsunamis. For instance, by monitoring fault lines, NISAR can identify areas of
slow movement or locked faults, providing insights into potential seismic
risks. Its all-weather imaging capability ensures that data remains available
during cloud cover or darkness, critical for assessing flood zones or storm
impacts. The satellite’s near real-time data will empower disaster response
teams to act swiftly, potentially saving lives and reducing economic losses.
For example, in the aftermath of the magnitude-8.8 earthquake off Russia’s Far
East coast on July 30, 2025, NISAR’s data could have aided in mapping affected
areas, even under adverse weather conditions.
Climate Monitoring and
Environmental Stewardship
NISAR will provide
critical data on climate change impacts, particularly in the cryosphere. Its
left-facing instruments will study the Antarctic ice sheet, tracking melting
and growth patterns to refine models of sea-level rise. The satellite will also
monitor glaciers, permafrost, and sea ice, contributing to a better
understanding of the carbon cycle and climate dynamics. By mapping wetlands and
forests, NISAR will assess ecosystem disturbances and support biodiversity
conservation efforts.
Agriculture and Resource
Management
NISAR’s data will enhance
agricultural productivity by monitoring soil moisture, crop growth, and land
use changes. Farmers and policymakers can use this information to optimize
irrigation, assess crop health, and plan sustainable agricultural practices.
The satellite’s ability to map surface water resources will also aid in water
management, particularly in water-scarce regions.
Infrastructure and Urban
Planning
By detecting subtle land
movements, NISAR will help assess the integrity of critical infrastructure such
as levees, dams, and aqueducts. This capability is vital for preventing
failures that could lead to catastrophic consequences. Urban planners can use
NISAR’s data to monitor ground subsidence and ensure resilient city
development.
Global Accessibility and
Societal Benefits
NISAR’s open-data policy
will democratize access to high-resolution Earth observation data, benefiting
developing nations that lack advanced satellite systems. This accessibility
will support global research, policy-making, and disaster preparedness, aligning
with India’s vision of being a “Vishwa Bandhu” (global partner) as articulated
by Prime Minister Narendra Modi and Union Minister Jitendra Singh.
A Beacon of Hope Amidst
Global Challenges
The successful launch of
NISAR comes at a time of geopolitical and economic uncertainty, notably with
the announcement of 25% tariffs on India by U.S. President Donald Trump. Amid
this gloom, the NISAR mission stands as a symbol of hope, showcasing the power
of collaboration between the world’s oldest and largest democracies. The
mission’s success underscores the resilience of the U.S.-India partnership,
which has weathered challenges to deliver cutting-edge science for global
benefit. As ISRO Chairman V. Narayanan noted, NISAR will generate a “tremendous
amount of data” daily, serving decision-makers, scientists, and disaster
managers worldwide. This echoes the vision of Dr. Sarabhai, who saw space as a
tool for uniting humanity through shared knowledge and progress.
Conclusion
The NISAR mission,
launched on July 30, 2025, marks a historic milestone in the ISRO-NASA
partnership, building on the legacy of pioneers like Dr. Sarabhai, Dr. Bhabha,
Prof. Dhawan, and Dr. Chitnis. Over the next three months, as NISAR completes
its deployment and commissioning phases, it will transition into a powerful
tool for observing Earth’s complex processes. By providing high-resolution,
all-weather data, NISAR will revolutionize disaster mitigation, climate
monitoring, agriculture, and infrastructure management, benefiting not only
India and the United States but also the global community. As the satellite
begins beaming images in late October 2025, it will carry forward the spirit of
the 1975 SITE program, using space technology to address humanity’s most
pressing challenges. In an era of global uncertainties, NISAR stands as a
testament to what two democracies can achieve when united by a shared
commitment to science and the collective good.
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