An exact duplicate of the Voyager I craft passes by Earth; how close for our equipment to detect it?

[Max_S]

What angle is it coming at? Most of our instruments are designed to pick up comets and asteroids not too far off the ecliptic plane.

Related:

When - and how - would we detect an interstellar object the size of the Moon headed right at us?

Supposing a Moon-like object approaches the Solar System on a collision path with Earth (or the Moon!). When and how do we detect it? We can assume this object is spherical and roughly 3,500 km in diameter. With my basic understanding of light and telescopy, you can detect such an object when enough light from our Sun is reflected off the object, into the mirrors of a telescope, and into your eyes (or a sensor). The unit of measurement of this light is called apparent magnitude (\text{m}), a r…

~Max