| Summary: | The HH80-81 system is one of the most powerful jets driven by a massive protostar. We present new near-infrared (NIR) line imaging observations of the HH80-81 jet in the H _2 (2.122 μ m) and [Fe ii ] (1.644 μ m) lines. These lines trace not only the jet close to the exciting source but also the knots located farther away. We have detected nine groups of knot-like structures in the jet including HH80 and HH81 spaced 0.2–0.9 pc apart. The knots in the northern arm of the jet show only [Fe ii ] emission closer to the exciting source, a combination of [Fe ii ] and H _2 at intermediate distances, and solely H _2 emission farther outwards. Toward the southern arm, all the knots exhibit both H _2 and [Fe ii ] emission. The nature of the shocks is inferred by combining the NIR observations with radio and X-ray observations from the literature. In the northern arm, we infer the presence of strong dissociative shocks, in the knots located close to the exciting source. The knots in the southern arm that include HH80 and HH81 are explicable as a combination of strong and weak shocks. The mass-loss rates of the knots determined from [Fe ii ] luminosities are in the range ∼3.0 × 10 ^−7 –5.2 × 10 ^−5 M _⊙ yr ^−1 , consistent with those from massive protostars. Toward the central region, close to the driving source of the jet, we have observed various arcs in H _2 emission that resemble bow shocks, and strings of H _2 knots that reveal traces of multiple outflows.
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