This paper presents upgrades for the Passive Active L-band Sensor (PALS) microwave instrument. PALS is the primary calibration and validation airborne instrument for the Soil Moisture Active Passive (SMAP) mission. PALS has been successfully deployed in the field for more than a decade, increasing in size, weight and complexity. Currently, a state-of-the-art upgrade is being carried out to ensure the instrument is ready to meet current and future science requirements at the same time that is more portable and easy to deploy.