- What is GLOWS?
GLObal solar Wind Structure (GLOWS) is a non‑imaging, single‑pixel Lyman‑α photometer riding on NASA’s new IMAP (Interstellar Mapping and Acceleration Probe) spacecraft. It counts far‑UV photons at 121.6 nm scattered by interstellar hydrogen (the “helioglow”) to track how the solar wind changes with latitude and over the solar cycle. imap.princeton.edu - Launch snapshot:
IMAP lifted off Sept. 24, 2025 at 7:30 a.m. EDT (11:30 UTC) on a SpaceX Falcon 9 from LC‑39A, ridesharing with NOAA’s SWFO‑L1 and NASA’s Carruthers Geocorona Observatory. Separation and early operations were nominal; IMAP is cruising to Sun–Earth L1 (~1 million miles/1.5 million km). NASA - Where it will operate & when science starts:
IMAP heads for a halo/Lissajous orbit around L1, with arrival expected by January 2026. First science is anticipated soon after commissioning; Polish science outreach reports first data around February 2026. NASA - Who built GLOWS?
Designed and built by Poland’s Space Research Center of the Polish Academy of Sciences (CBK PAN)—the first instrument fully developed in Poland for a NASA mission. Integration was completed at Johns Hopkins APL in 2024. imap.princeton.edu - How it works (nuts & bolts):
Light enters a baffle + collimator, passes a narrowband Lyman‑α filter, and is counted by a channel electron multiplier (CEM)—about 1,000 photons per second when scanning the sky as IMAP spins. The spin axis is retargeted daily, letting GLOWS build up global maps. imap.princeton.edu - Software & operations:
Onboard software was developed by KP Labs (Poland) using RTEMS, with resilient data handling (histograms, archiving, preprocessing) to send compact, science‑ready counts to Earth. kplabs.space - Important nuance (helium channel):
Early design papers and catalogs described GLOWS with two spectral channels—hydrogen Lyman‑α (121.6 nm) and helium at 58.4 nm—via separate detectors (LαD and HeD. As flown, the official instrument pages from Princeton/CBK emphasize Lyman‑α only; NASA’s January 2025 blog still mentioned helium, which may reflect an earlier concept. Public, post‑integration pages don’t confirm a flight helium channel. GLOWS
Deep dive: GLOWS, the helioglow, and why IMAP needs it
What problem does GLOWS solve?
The Sun’s solar wind doesn’t blow uniformly. It varies with heliographic latitude (equator vs. poles) and evolves across the ~11‑year solar cycle, but we lack continuous, global context—especially at high latitudes. GLOWS tackles this by measuring the helioglow, the faint EUV light emitted when interstellar neutral hydrogen gets excited by solar Lyman‑α photons and re‑emits them. Mapping the brightness distribution of this glow reveals how much interstellar hydrogen is present along different sightlines—an indirect but powerful tracer of solar‑wind structure, ionization, and radiation pressure. imap.princeton.edu
How the instrument actually works
GLOWS is deliberately simple and rugged: a single‑pixel photometer optimized to count 121.6‑nm photons with high fidelity. A baffle suppresses stray light; a straw‑like collimator narrows the field of view; a narrowband filter passes only Lyman‑α; and a CEM multiplies electrons produced by the photoelectric effect so each photon becomes a crisp electrical pulse. As IMAP spins (~4 rpm), the instrument sweeps thin slices of sky; daily spin‑axis repointing stitches those slices into an all‑sky map over time—ideal for watching the solar wind evolve through solar maximum and beyond. imap.princeton.edu
What GLOWS will measure—and why that matters
By tracking the helioglow’s intensity variations, GLOWS will:
- Reconstruct the solar wind’s global latitudinal structure, including the poorly sampled polar regions;
- Quantify solar radiation pressure acting on neutral hydrogen, a key force shaping hydrogen distributions;
- Monitor solar‑cycle evolution of the glow to reveal how changing solar output alters interstellar gas in the heliosphere.
These results give crucial context to IMAP’s particle and field measurements and sharpen models used in space‑weather forecasting. GLOWS
Launch, cruise, and commissioning timeline
IMAP launched Sept. 24, 2025 (07:30 EDT) on Falcon 9 from Kennedy LC‑39A, alongside NOAA’s SWFO‑L1 and NASA’s Carruthers Geocorona Observatory. Within hours, all three spacecraft reported healthy signals. IMAP is now headed to L1 (~1 million miles) and will start commissioning en route and on arrival; NASA targets arrival by January 2026. After instrument checkouts and calibrations, science operations begin; Polish outreach indicates first data could appear as soon as February 2026. NASA
A milestone for Poland’s space sector
CBK PAN led GLOWS end‑to‑end—optics, electronics, power, flight software, and test campaigns—marking the first NASA‑flown instrument fully designed and built in Poland. The team integrated GLOWS at Johns Hopkins APL in 2024; KP Labs contributed robust onboard software to manage pulse shaping, histogramming, and data integrity under deep‑space conditions. imap.princeton.edu
How GLOWS fits into the rest of IMAP
IMAP carries 10 instruments across electrons, ions, energetic neutral atoms, dust, and fields. As a context imager for the helioglow, GLOWS complements:
- IMAP‑Lo / IMAP‑Hi / Ultra (ENA imagers) that remotely sense the heliosphere’s boundary,
- SWE / SWAPI / CoDICE / HIT (in‑situ plasma and ion composition),
- MAG (magnetometers) and IDEX (interstellar dust).
Together, they provide a Sun‑to‑heliosphere picture with both local sampling and global imaging. NASA Science
The helium question: design vs. as‑flown hardware
Early IMAP documentation and catalogs described two GLOWS channels—Lyman‑α (H) and 58.4‑nm (He)—via separate detectors (LαD and HeD). However, current Princeton IMAP and CBK PAN instrument pages emphasize Lyman‑α only, and the flight configuration publicly described after integration does not detail an operational helium detector. NASA’s January 2025 blog referred to “hydrogen and helium,” likely echoing the earlier concept. Until the team publishes a definitive flight‑hardware note, readers should assume Lyman‑α is the primary (and possibly sole) channel flown. NASA Science
What to watch next
- Cruise & L1 insertion: IMAP will continue its transfer and begin L1 operations by January 2026, maintaining a steady spin and daily Sun‑ward repointing to power instruments like GLOWS. NASA Science
- Commissioning & first‑light: GLOWS will be powered on and tuned during commissioning; first‑light helioglow maps may arrive in early 2026, enabling the first latitudinal snapshots near solar maximum. imap.princeton.edu
- Space‑weather relevance: IMAP supports real‑time solar‑wind and energetic‑particle observations; GLOWS’ global context should feed better boundary conditions for models that inform space‑weather alerts. NASA Science
Glossary (quick refresher)
- Helioglow: Faint EUV emission from interstellar neutral hydrogen excited by solar Lyman‑α photons; its brightness traces hydrogen density and ionization sculpted by the solar wind. imap.princeton.edu
- Lyman‑α (121.6 nm): A far‑UV line of hydrogen; blocked by Earth’s atmosphere, so it must be observed from space. Science in Poland
- L1 (Sun–Earth Lagrange Point 1): A gravitational balance point ~1 million miles (1.5 million km) sunward of Earth; great for uninterrupted solar and heliospheric monitoring. NASA
Sources & further reading
- NASA press & blogs for launch confirmation and mission status (liftoff, L1 cruise, power/spin): NASA
- Princeton IMAP instrument pages for authoritative GLOWS descriptions and technical overviews: imap.princeton.edu
- CBK PAN (instrument page) for build details and objectives; Princeton news for Polish‑built milestone and integration timeline: GLOWS
- KP Labs on flight software and reliability: kplabs.space
- Early design references (2018 mission paper; instrument catalog) indicating planned He (58.4 nm) capability: Space Physics at Princeton
