ISRO’s EOS-08 Launch Marks Leap in India’s Space Odyssey

ISRO plans to launch the 8th Earth Observation Satellite-8 (EOS-8), using its third developmental small satellite launch vehicle (SSLV-D3) on August 16, the day after India’s Independence Day. The launch is set for a one-hour window beginning at 9:17 am (IST), as announced in ISRO’s post on X. This will be the third and final test flight of the SSLV from Sriharikota. According to ISRO, this launch will complete the SSLV development project and lead to future missions by Indian industry and NewSpace India Limited (NSIL).

If the launch is successful, forthcoming SSLV missions will focus on the needs of the NSIL and the commercial market. The SSLV is a smaller and more efficient version of the PSLV. It can be assembled in just a few days with fewer people, while the PSLV takes over a month and needs more manpower. As a cost-effective launcher, the SSLV is expected to increase the number of ISRO’s commercial launches and help India expand its share in the global space launch services market, valued at $14.9 billion in 2023, and projected to grow at a rate of 14.6% from 2024 to 2030, according to ToI.

The main goal of EOS-08 is to create and develop a small satellite that incorporates new technologies needed for future missions. It also ensures that the instruments it carries work well with the satellite’s core system, known as the microsatellite bus, which is the basic framework of the satellite that provides such essential functions as power, communication and control, allowing the satellite to operate effectively in space.

EOS-08 AND ITS PAYLOADS

Mass and Power: The EOS-08 satellite weighs about 175.5 kg and is built to produce 420 watts of power. It is expected to operate for one year.

Payloads

1. Electro Optical Infrared Payload (EOIR): This payload takes images in the mid-wave IR (MIR) (3 to 5 micrometres) and long-wave IR (LWIR) (8 to 12 micrometres) ranges, working both day and night. It helps with various tasks, such as satellite surveillance, monitoring disasters, tracking the environment, detecting fires, observing volcanic activity and assessing incidents at industrial sites and power plants

2. Global Navigation Satellite System-Reflectometry Payload (GNSS-R): This payload is used for remote-sensing tasks, such as analysing ocean surface winds, assessing soil moisture, studying the cryosphere in the Himalayan region, detecting floods and monitoring inland water bodies

3. SiC UV Dosimeter: This device measures UV radiation, especially for the Gaganyaan mission and acts as an alarm for high levels of gamma radiation.

TECHNICAL ADVANCEMENTS

The EOS-08 satellite includes significant upgrades, particularly with its new integrated avionics system, known as the communication, baseband, storage and positioning (CBSP) package. This system combines multiple functions into a single unit using commercially available components, allowing for efficient

communication and data management while providing up to 400 GB of storage. By integrating these functions, the CBSP package reduces the overall weight and complexity of the satellite’s systems, enhancing its efficiency.

Additional tech improvements include a structural panel with a built-in circuit board, a battery inside, a micro-DGA (dual gimbal antenna), a phased array antenna (M-PAA) and a flexible solar panel. These parts are important for testing new technology, making EOS-08 a key achievement in ISRO’s space missions.

i. A Micro-DGA (dual gimbal antenna) is a type of antenna that can move in two directions, allowing it to track satellites more accurately. This helps ensure strong communication signals during the satellite's operations.

ii. A phased array antenna (M-PAA) uses multiple small antennas that can change their signal direction quickly. This allows the satellite to communicate with different targets without moving the whole antenna

ISRO’s successful launch of the SSLV-D3/EOS-08 mission will allow for regular operations, strengthening India’s space capabilities and enhancing its earth observation and remote-sensing systems. ISRO’s successful launch of the SSLV-D3/EOS-08 mission will allow for regular launches, improving India’s space capabilities and enhancing its earth observation and remote-sensing systems.

WHAT EXACTLY IS AN EOS?

Earth observation satellites (EOSes) are like our eyes in the sky, keeping watch over our planet. These satellites are designed to observe and gather information about Earth from space. While some are used for military purposes, many others play a crucial role in understanding and managing our environment. They help us track such things as:

o Ocean health: Measuring how salty the ocean is

o Ice levels: Determining how thick ice caps and glaciers are

o Agriculture: Monitoring the health of our crops

o Air quality: Assessing the quality of the air we breathe

The information these satellites collect is essential for protecting our environment, managing resources responsibly, responding to natural disasters and humanitarian crises and promoting sustainable development.

The most common types of satellites are Earth-imaging satellites, which capture images of Earth similar to aerial photos. Some Earth observation satellites can gather data without creating pictures, such as those using GNSS radio occultation (or shadowing).

DIFFERENT TYPES OF EOSES

EOSes can be grouped into two types based on how they gather images: Passive and active.

ü Passive satellites capture radiation that bounces off Earth’s surface, such as visible light and infrared. However, they usually cannot see through clouds

ü Active satellites, on the other hand, send energy down to Earth and measure the signals that come back. This allows them to gather information even when there are clouds

HOW EOSES GATHER DATA

EOSes travel in different orbits, giving various views of Earth. Most satellites cannot collect data all the time due to limits in power and storage. Some provide regular and reliable data, while others gather

smaller amounts over longer periods. The data is stored on the satellite until it can connect with a ground station to send it down. The time from when an image is taken to when it is available for download can range from a few minutes to a month, but this is getting faster with new technology. Since different companies own these satellites, there are many data providers, each with their own pricing.

ISRO has launched many remote-sensing satellites that are currently being used for various applications, such as agriculture, urban planning, rural development, mineral prospecting, environment monitoring, forestry, ocean resources mapping and disaster management. There are 13 satellites in Sun-synchronous orbit and four in geostationary orbit.

SSLV FOR 500-KM PLANAR ORBIT

The SSLV is a three-stage rocket designed with three solid-fuel stages and a liquid-fuel stage called the velocity trimming module (VTM) that finetunes the final speed. The VTM makes precise adjustments by using small bursts of liquid fuel to control the rocket’s speed and direction, ensuring that the satellite reaches its exact orbit. This setup helps small satellites reach their intended orbits effectively and efficiently.

The SSLV is 2 metres wide and 34 metres long, weighing around 120 tons at launch. It can carry a satellite weighing about 500 kg into a 500-km high planar orbit—an orbit that lies flat on a single, imaginary surface, such as a disk—when launched from the SDSC/SHAR. An example of a planar orbit is when a satellite orbits Earth, it can move in a path that does not go up or down but stays on that flat surface around the planet. This makes the orbit ‘planar’.

The SSLV stands out for its low cost, quick turnaround time and ability to carry multiple satellites. It can be launched on demand and requires minimal infrastructure, making it highly efficient and flexible.

(The author of this article is a Defence, Aerospace & Political Analyst based in Bengaluru. He is also Director of ADD Engineering Components, India, Pvt. Ltd, a subsidiary of ADD Engineering GmbH, Germany)

(Disclaimer: The views expressed above are the author's own and do not reflect those of DNA)