ALOS-2

ALOS-2 (Advanced Land Observing Satellite-2, "Daichi-2") is an L-band synthetic aperture radar mission operated by the Japan Aerospace Exploration Agency (JAXA) ^[1]. Built by Mitsubishi Electric Corporation under JAXA contract, the satellite was launched on 24 May 2014 aboard an H-IIA launch vehicle ^[1]. The spacecraft has a mass of approximately 2,100 kg and operates in a sun-synchronous sub-recurrent orbit at 628 km altitude with a 97.9-degree inclination, a 14-day repeat cycle, and a descending node local time of 12:00 ^[1].

ALOS-2 carries a single primary instrument, the Phased Array type L-band Synthetic Aperture Radar-2 (PALSAR-2), operating at a centre frequency of 1,257.5 MHz (wavelength approximately 23.84 cm) ^[2]. PALSAR-2 supports six resolution modes from 1-metre Spotlight through 490-kilometre-swath ScanSAR, and is capable of full polarimetric (quad-pol), dual-pol, and single-pol acquisitions ^[2]. The combination of L-band wavelength and wide-swath operation makes the mission particularly suited to tropical forest disturbance monitoring, surface deformation mapping via interferometry, and disaster response imaging in cloud-covered or smoke-obscured regions.

ALOS-2 succeeded the original ALOS (Daichi, 2006-2011) and substantially improved on its predecessor by adding right-and-left looking capability and expanding maximum swath width from the original PALSAR to up to 490 km ^[3]. The satellite exceeded its 5-year primary design life (goal: 7 years) and remained in extended operations as of 2026. JAXA launched ALOS-4 (Daichi-4) on 1 July 2024 as the successor mission ^[4]; both satellites operated concurrently during the transition period.