https://xiaolan.in/missions/Recent content in Missions on Xiaolan XuHugoenhttps://xiaolan.in/missions/aquarius/Mon, 01 Jan 0001 00:00:00 +0000https://xiaolan.in/missions/aquarius/Aquarius is where my freeze–thaw work began. As first author, I developed and validated the first L-band detection of landscape freeze/thaw state from Aquarius’ backscatter data — showing that a scatterometer could reliably flag the frozen/thawed switch across the boreal and Arctic land surface, the signal that marks spring onset and frost timing. That detection method became the basis for the operational SMAP freeze/thaw science product I now lead — a direct line from an early-career research result to a mission deliverable.https://xiaolan.in/missions/cygnss/Mon, 01 Jan 0001 00:00:00 +0000https://xiaolan.in/missions/cygnss/I built JPL’s operational Level-3 soil-moisture product for CYGNSS, and I lead an ongoing NASA ROSES-funded effort — as PI, since 2021 — to improve that retrieval and add a vegetation optical depth product using CYGNSS v3 data. Earlier, I was Co-I on the mission’s original soil-moisture algorithm and validation effort (2018–2021). It’s the same soil-moisture question as SMAP, answered through a completely different measurement: navigation-satellite signals reflected off the land surface instead of a dedicated radiometer.https://xiaolan.in/missions/new-mission-concept/Mon, 01 Jan 0001 00:00:00 +0000https://xiaolan.in/missions/new-mission-concept/This new mission concept has had me as algorithm contributor for over a decade, across several proposal rounds — CubeSat, EVI, and EVM announcements of opportunity, none yet funded. My side of it is the retrieval physics: how a P-band signal scatters off soil and vegetation, and what that means for sensing root-zone moisture and snow water equivalent at a depth L-band can’t reach. Two funded precursor studies have supported that work directly, as Co-I: a signals-of-opportunity concept for root-zone soil moisture and snow, and the theoretical basis for P-band SWE retrieval.https://xiaolan.in/missions/nisar/Mon, 01 Jan 0001 00:00:00 +0000https://xiaolan.in/missions/nisar/My NISAR work sits inside SMAP. Since 2024, I’ve been building the active-passive soil-moisture algorithm that fuses SMAP radiometer data with NISAR’s L-band SAR — the retrieval NISAR’s soil-moisture products are expected to draw on once the mission is on orbit. I lead this as PI of a five-year NASA ROSES USPI award, and it’s the direct continuation of the freeze–thaw and soil-moisture work I’ve done under SMAP. I also contribute to the mission’s snow side: as Co-I on a NASA-funded project, I help build a multi-frequency InSAR phase data-assimilation framework for tracking seasonal snow water equivalent, aimed at the kind of repeat-pass InSAR NISAR is expected to support.https://xiaolan.in/missions/smap/Mon, 01 Jan 0001 00:00:00 +0000https://xiaolan.in/missions/smap/I’ve worked on SMAP since before launch in 2015, starting in graduate school. I lead development of the mission’s L-band freeze–thaw algorithm — from the original detection method, first validated on Aquarius, to the operational Level-3 Freeze/Thaw data record NASA distributes today. I’m first author on that data product and on the JSTARS paper introducing the Aquarius-based detection method it grew out of. I’m now carrying that L-band expertise into the next era: as PI of a five-year NASA ROSES award, I lead development of the joint SMAP–NISAR active-passive soil-moisture algorithm — the retrieval method the mission will use once NISAR L-band SAR data is available to fuse with SMAP’s radiometer measurements.