India–Bhutan SAT: connect two payloads to a ground team

India–Bhutan SAT is the joint spacecraft cataloged as INS-2B. ISRO records its successful deployment during the PSLV-C54 mission in November 2022. NanoMx, the multispectral optical imaging payload, was developed by India’s Space Applications Centre. The APRS digipeater — open definition was developed jointly by Bhutan’s Department of Information Technology and Telecom and ISRO’s U R Rao Satellite Centre. These contributions have distinct responsibilities within one mission.

A radio relay and an optical imager produce different evidence. Successful message retransmission does not prove image calibration; a recognizable landscape does not prove that every relay mode works. A mission review should report the tests and results for each payload, then assess the shared support systems that make both possible, including electrical power, pointing, communication and ground operations.

The India–Bhutan SAT ground station in Thimphu was inaugurated on 13 March 2023. ISRO described its role in direct reception and processing of imagery for Bhutan. GovTech’s later technical presentation discusses attempts to use the data for landslide mapping and urban-settlement work, while explicitly identifying limits associated with spatial resolution. That is valuable engineering feedback: the ability to acquire an image is not equivalent to suitability for every mapping task.

Consider a simplified sixty-meter-wide ground cell containing a six-meter-wide road. The road and neighboring surfaces contribute to one sample; the cell cannot be treated as sixty meters of pure road. Better ground sampling can help separate features, but optical blur, contrast, shadows and viewing geometry also matter. Enlarging the picture on a screen adds display pixels without recovering measurements the sensor never made.

A pixel can mix several ground features

If a planning team needs to map an entire valley, broad regional coverage may be helpful. If it needs individual road edges, it needs a different level of detail and validation. Write those requirements before choosing a camera or promising an application. Ground checks can reveal that a seemingly sharp boundary in an image belongs to a shadow rather than the feature of interest.

GovTech’s SANOG presentation lists June 2024 as INS-2B’s end of life. That dated account should not be turned into a claim of a currently available live service. The archived observations and engineering experience can still inform later work. A good follow-on requirement states not just pixel size, but the feature to be detected, acceptable error, required area and delivery time. The sixty-meter example is illustrative and is not asserted as NanoMx’s actual specification.