New message: India's EOS-05 (GISAT-1A) high-orbit imaging satellite successfully launched, with successful rocket stage!

This is India's first truly meaningful high-orbit, high-resolution optical remote sensing satellite.

At 02:55 IST (05:25 Beijing Time), GSLV-F17 ignited and lifted off.

About 18 minutes into flight, the EOS-05 satellite accurately entered its intended sub-synchronous transfer orbit: perigee 170 km, apogee 28,934 km, inclination 19.28°.

ISRO (Indian Space Research Organisation) chairman confirmed that the rocket achieved orbit insertion within required accuracy;

This marks the 19th flight in the GSLV series, rectifying the failure of the 2021 EOS-03 (GISAT-1) launch.

However, the mission is not yet complete: rocket success does not equal satellite operational readiness.

Over the next several days, the satellite will rely on its own chemical propulsion system to perform multiple burns to raise its orbit and reduce inclination, gradually reaching the 35,786 km geostationary equatorial orbit;

Following this, payload activation and in-orbit calibration must be completed before it enters formal operational use months later.

India’s EOS-05 satellite functions are similar to China’s Gaofen-4 and Fengyun-4 satellites.

Key differences:

1. Spatial Resolution

EOS-05 achieves optimal resolution of 42 meters, compared to Gaofen-4’s 50 meters;

Yet they employ different imaging systems: EOS-05 uses pushbroom scanning for wide-area coverage;

Gaofen-4 employs staring cameras capable of rapid, repeated imaging over small, specific regions.

Fengyun-4 has spatial resolution in the hundreds of meters to kilometers, not targeting fine ground details; its primary focus is atmospheric parameters.

2. Spectral and Day/Night Capability

Gaofen-4 includes a mid-wave infrared channel enabling nighttime imaging to detect fire heat sources;

Public data for EOS-05 primarily cover visible and near-infrared spectra, lacking mature infrared detection payloads;

Fengyun-4 has the strongest infrared capability but lowest resolution, focused on cloud-top temperature rather than ground targets.

3. Temporal Resolution (Revisit)

All three satellites are positioned in geostationary orbit, theoretically allowing continuous monitoring of fixed regions.

• EOS-05: Full South Asia disk takes about 30 minutes; interested smaller areas can be imaged as quickly as every 5 minutes.

• Gaofen-4: In staring mode, can achieve imaging at minute-level intervals over target areas.

• Fengyun-4: Full disk scan in 15 minutes; localized rapid scans every 1 minute, tailored for short-term weather forecasting.

4. System Maturity

• China: Gaofen-4 has been in long-term operational use; Fengyun-4 has already deployed three satellites (A/B/C), forming a complete operational system with global data sharing services.

• India: EOS-05 is the second attempt along this path; the prototype failed directly during launch. Even if this launch succeeds, the satellite still requires orbital raising and payload calibration—true operational deployment will take several more months.

5. Mission Orientation

EOS-05 essentially targets Gaofen-4’s role—high-orbit land remote sensing. In contrast, Fengyun-4 is an entirely different type of dedicated meteorological satellite and should not be directly compared with EOS-05 using resolution metrics alone.

Original source: toutiao.com/article/1875359633399882/

Disclaimer: The views expressed in this article are solely those of the author.