Which of the following is not the satellite launched by India?

The correct option is Explorer.

To understand why this is the correct choice, let us look at the details of each satellite listed in the options:

1. Explorer:
Explorer 1 was the first satellite successfully launched by the United States in 1958. It was part of the US Explorer program and was not launched by India.

2. APPLE (Ariane Passenger Payload Experiment):
APPLE was India's first experimental communication satellite. It was launched successfully by the Indian Space Research Organisation (ISRO) on June 19, 1981.

3. Bhaskar:
Bhaskara-I and Bhaskara-II were experimental remote sensing satellites built by ISRO. Bhaskara-I was launched on June 7, 1979, and Bhaskara-II was launched on November 20, 1981.

4. INSAT (Indian National Satellite System):
INSAT is a series of multipurpose geostationary satellites launched by ISRO to satisfy India's telecommunications, broadcasting, meteorology, and search and rescue operations.

Therefore, Explorer is not a satellite launched by India, making it the correct option.