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India to launch SSLV-D2 tomorrow from Satish Dhawan spaceport

The small lift carrier rocket will undergo modifications after SSLV-D1 failure

Launch Infographics: SSLV-D2

The second launch of India's new SSLV – Small Satellite Launch Vehicle rocket, the SSLV-D2, is due to take place on February 10, 2023, at 09:18 IST (03:48 GMT) from the Satish Dhawan Space Center in Sriharikota. The three-stage rocket is intended to place the EOS-07, Janus-1 and AzaadiSAT-2 satellites in a circular orbit of 450 km, inclined at 37.2 degrees and with a launch azimuth of 135 degrees. This will be the 85th Orbital launch from India, and First in 2023.

SSLV-D2 at FLP, Sriharikota (Photo: ISRO)

The payload including the 156.3 kg EOS-07 satellite and the two passenger satellites. New experiments include mm-Wave Humidity Sounder and Spectrum Monitoring Payload. Janus-1, a 10.2 kg satellite belongs to ANTARIS, USA. A 8.7 kg satellite AzaadiSAT-2 is a combined effort of about 750 girl students across India guided by Space Kidz India, Chennai. the total mass is greater than the sum of the three satellites (about 175 kg), but it could be counting the adapter or the equipment bay.

Equipment section and payload adapter

The Small Satellite Launch Vehicle, or SSLV, "is fully prepared for launch with the Indian space agency ISRO targeting an early February launch carrying three payloads," announced the country's official media on social media. The rocket is capable of 500 kg low-orbit 'launch on demand' with low cost, low turnaround time and flexibility to accommodate multiple satellites and requires minimal launch infrastructure. The rocket is 34 meters long, 2 meters in diameter, and has a launch mass of about 119 tons. It has three stages of solid propulsion and a 'terminal velocity module' (high precision aiming upper stage).

The satellites



EOS-07 is an Earth observation satellite based on the Microsatellite-SSB (SSB-1) chassis with a mass of 156.3 kg designed and developed by ISRO. New experiments include a millimeter-wave moisture sonar and a spectrum monitoring sensor. Its equipment aims to meet user demands for cadastral-level cartographic systems, urban and rural management, coastal land use and regulation, utility mapping, development and various other GIS applications. The satellite carries two payloads, a mid-wavelength infrared (MWIR in the wavelength range of 3.0 to 5.0 μm) and a long-wavelength infrared (LWIR, in a wavelength of 8. 0 to 14.0 μm), with a terrestrial resolution of 6 meters. The spacecraft's projected lifetime should be ten months.


JANUS-1 (Antaris Space)

JANUS-1 is a 11.5 kg 6U-type cubesat technical demonstration satellite for the efficiency and cost-effectiveness of the Antaris platform, and carries five payloads running its SatOS™ satellite software in orbit. XDLINX Labs and Ananth Technologies served as the primary satellite manufacturing partners with ATLAS Space Operations providing ground station services.

Antaris, a space software provider, announced that JANUR is the first satellite to be fully conceived, designed and manufactured using its end-to-end software, involving eight organizations in seven countries collaborating virtually through its cloud-based platform that features open APIs. and open source core elements. The project was completed in 10 months, with a cost savings of 75% over comparable missions. Based on data captured during construction, Antaris anticipates that future spacecraft missions could be ready for launch in as little as six months. The company recently open-sourced the SatOS Payload Software Development Kit (SDK), which allows users to effectively integrate payloads into satellites using the code. Furthermore, “The satellite industry has historically lagged behind the technology industry in adopting software-as-a-service models,” said Brad Bode, chief technology officer for ATLAS Space Operations. “The SaaS platform is a long-awaited approach to satellite design, simulation and operation and a perfect complement to our own GSaaS model, or Ground Software as a Service. We are excited to be a part of the historic mission.”

“Ananth Technologies is pleased to collaborate with Antaris on this new demonstration project,” added Dr. Subba Rao Pavuluri, President and Managing Director of the company. “We support their mission to drive collaboration across the space economy and see tremendous potential in this new approach to satellite design and operations. The build process was highly efficient, even for a complex project with multiple payload suppliers from around the world.”

Payload and subsystem technology providers, including AICRAFT, Netra, Morpheus Space, Sayari Labs Kenya, SpeQtral, Transcelestial and Zero-Error Systems (ZES), will conduct testing of IoT communications, experimental advanced laser communications, radio and machine communications. learning, and inference research in orbit. A virtual twin of the satellite running on Antaris TrueTwin™ technology is ready for comparisons with the real set's performance.

Antaris enabled rapid production through an agile building block approach unique to the company's software platform: The cloud-based web interface facilitates design and configuration from a catalog of components, subsystems and reference designs. The platform features built-in API integrations with multiple vendors, including ground station operators. TrueTwin™ high-fidelity simulation technology allows designers to mirror and test the satellite configuration by running identical code in virtual and physical environments with API-driven access and optional on-loop hardware support. The complete SatOS™ software stack manages core chassis responsibilities while combining 'multi-assist' payloads and embedded computing with support for real-time operating systems, Linux, artificial intelligence (AI/ML) workflows and the 3rd. • Well-documented APIs and an open source SDK allow partners to quickly integrate their payloads into the chassis.

Antaris co-founders Tom Barton and Karthik Govindhasamy, who previously worked together in executive leadership roles at Planet Labs, created Antaris in 2021 as "a response to their frustration with the exorbitant cost and timelines typically associated with satellite development" . The company's founding engineering team "brings decades of prior professional experience from industry pioneers Planet Labs, Microsoft, CoreOS and Apple." “With thousands of satellites expected to be launched over the next three years, we are facing a shortage of satellite engineering talent, along with the historical legacy of waste and inefficiency across the supply chain,” noted Govindhasamy. “We started Antaris with a mission to eliminate this inefficiency and empower space engineering talent through a software platform designed to simplify the design, simulation and operation of satellites. We thank our partners for being our first and most enthusiastic users of the Antaris software and we look forward to a successful launch in the coming days.”

“This is a tremendous time for the space industry,” said co-founder Barton. “Satellite development has historically been slow and extremely expensive because of proprietary hardware and software, excessive vertical integration and outdated interfaces, APIs and protocols. Antaris changed all that. Our cloud-based platform has enabled constellation sponsors, designers, component suppliers and manufacturers from around the world to seamlessly come together and collaborate to prepare a satellite for launch in just months, not years, from start to finish. Nothing like this has ever been done before.”


AzaadiSAT-2 (SKI)

The AzaadiSAT is an 8U-sized cubesat that weighs 8.7 kg. He carries 75 different payloads, each weighing around 50 grams and performing 'femto-experiments'. Students from rural areas across the country were guided to build these loads and integrated by the student team of “Space Kidz India”. Payloads include a UHF-VHF transponder working on radio frequency to enable voice and data transmission for ham radio operators, a solid state PIN diode based radiation counter to measure ionizing radiation in orbit, a long range transponder and a selfie camera. The ground system developed by 'Space Kidz India' will be used to receive data from this satellite.

Lessons from SSLV-D1 mission


The launch of the D-2 aims to check the modifications made after the failure of the first flight of the model, made on August 7 last year. During the mission, several defects were verified: Basically, the third stage separation mechanism (explosive) “touched” the vehicle with more force and for longer than expected, saturating the onboard accelerometers and causing the flight to disable them by giving erroneous readings. The accelerometers still worked fine after the vibrations subsided, so if the software had anticipated this, they could have been used later. Anyway, the software was operating in open loop, not receiving data from external sensors,

Finally, the VTM stage was purposely not deployed due to concerns that it would be detrimental to achieving orbit after an open-loop flight. Larger residuals and VTM deviation led to an underperformance velocity of ~56m/s.

Modifications for the second flight

Separation System Change – The separator mechanism has been modified for smoother actuation, and structural changes to more quickly dampen excessive oscillation. The flight logic was also modified, mainly relying on accelerometers to recover after initial transients and allowing the VTM to function in some circumstances that may not harm the mission in case of ascent failures. The separation system between the second and third stages was based on a circular expandable bellows system that shears the rivets and provides axial separation speed. This system has been replaced by the proven Marman band system for separation and springs to provide axial separation with speed. The new system generates less shock and is already used.

Logic in inertial equipment in Fault Detection & Isolation (FDI) system based on accelerometer threshold is modified to evolve a more realistic approach based on data generated through system level tests, integrated separation tests and flight . The check of the accelerometer residual logic in the Inertial Navigation System (INS) has been modified to deal with transient events. The moving average window has been modified so that, in case of failure of several sensors in the MINS, a longer duration check is implemented before setting the save mode.

The dynamic characterization and design modification of structures has been adapted

in the assembly of the equipment bay (Equipment Bay – EB) and the satellite together with the VTM stage and the modified structural project to increase the frequency of the structures. Modifications to the EB and satellite decks were implemented to minimize the response to the observed excitations.

NaVIC – in the event of failure of the inertial system sensors, the mission will proceed using NavIC navigation data in a closed-loop guidance scheme. The VTM stage will have a loop to rescue mode: in case of failure of inertial sensors and unavailability of data from the Indian satellite navigation system NavIC (for more than 10 seconds), an open loop heading guidance will be performed. The propulsive capacity of the VTM will be considered in this rescue mode as well and the propellants will be operated to guarantee the minimum perigee necessary for the mission.

SSLV vs PSLV (the Workhorse of ISRO)


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