---
title: CARMENES-PLUS Project
url: https://www.emergentmind.com/topics/carmenes-plus-project
type: topic
---

# CARMENES-PLUS Project

The CARMENES-PLUS Project is an advanced instrumental and scientific upgrade building upon the legacy of the original CARMENES survey at the 3.5-m Calar Alto telescope. It is focused on improving the detection and characterization of low-mass exoplanets around nearby M dwarfs through significant enhancements in spectrograph stability, calibration systems, data processing, and survey methodology. CARMENES-PLUS intensifies the pursuit of precise radial velocity (RV) measurements via innovative upgrades—particularly to the near-infrared (NIR) channel—and extends the collaborative scientific effort to maximize the discovery and physical characterization of exoplanets in the solar neighborhood.

## 1. Technical Advancements and Instrument Upgrades

CARMENES-PLUS implements key engineering upgrades, most notably to the NIR channel, targeting millikelvin-level temperature stability to reduce RV drifts. The main technical improvements include:

- **Continuous Flow Cryogenic Cooling System**: Upgrade from a discontinuous (on/off) to a continuously regulated (proportional) liquid nitrogen (LN₂) flow, governed by a PID control algorithm of the form $u(t) = K_P e(t) + K_I \int e(t) dt + K_D \frac{de(t)}{dt}$, where $e(t)$ is the temperature error. This decreases radiation shield temperature fluctuations from $\Delta T \sim 0.09$ K to $\Delta T \sim 0.002$ K [2509.17966].
- **Automatic Vacuum System**: Continuous maintenance of the vacuum in the cryogenic transfer lines to $<10^{-5}$ mbar, minimizing conduction losses and preventing frost formation affecting NIR stability.
- **Pressure Control Unit and Fixed-Dewar**: Automated PID feedback to stabilize the dewar pressure to $\sim0.421$–$0.426$ bar, eliminating thermal instabilities arising from daily manual dewar changes.
- **Removal of Mechanical Bottlenecks**: Elimination of a check valve in the feed line, thus preventing intermittent flow interruptions and ensuring smooth coolant delivery.

Collectively these measures reduce NIR intra-night RV scatter (from $\sim2.62$ m/s to $\sim0.67$ m/s in Fabry-Perot calibrations), lower the nightly zero-point scatter, and improve the median on-sky RV precision for slowly rotating M dwarfs from $8.8$ m/s to $6.7$ m/s [2509.17966].

## 2. Instrument Configuration and Calibration

The upgraded CARMENES-PLUS spectrograph retains the dual-channel, fiber-fed echelle design with simultaneous VIS and NIR operation ($0.52$–$1.71$ μm). Both channels are housed in thermally isolated, vacuum tanks to ensure ultra-stable conditions.

- **Calibration System Enhancements**: Replacement of individual Fabry–Pérot etalons with a single cryogenically-stabilized etalon for simultaneous VIS/NIR calibration, providing greater wavelength stability across the entire spectral range [2503.05501].
- **Customized Fiber Switches**: Introduction of a switch system for calibration fiber injection, enabling real-time calibration spectra acquisition from multiple sources, thus enhancing RV stability.
- **Intrinsic RV Precision**: Improvements bring NIR precision close to VIS channel performance (VIS channel typical scatter at $\sim4.3$ m/s), expanding the parameter space for exoplanet detection around faint, red M dwarfs (essential for habitable-zone planets).

## 3. Survey Goals and Methodology

CARMENES-PLUS builds upon the existing science objectives of detecting and characterizing Earth and super-Earth planets around a sample of $\sim300$–$400$ nearby M dwarfs via high-cadence, high-precision RV monitoring [1210.5465, 2302.10528].

- **Expanded Sample and Temporal Baseline**: The survey continues to update and expand high-cadence, multi-year observations, ensuring high sensitivity to both short- and long-period planetary signals, as well as secular and dynamical effects within planetary systems [2302.10528, 2407.11520].
- **Simultaneous Stellar Activity Characterization**: Broad wavelength coverage supports the measurement of chromatic RV indices, activity diagnostics (e.g., H$\alpha$, Ca II IRT, Paschen lines), and sophisticated modeling (including Gaussian processes) to disentangle stellar noise from Doppler shifts induced by planets [2203.00415, 2308.07685].

## 4. Scientific Impact and Results

CARMENES-PLUS has already demonstrated advancements in both instrumentation and scientific output:

- **Exoplanet Yield and Population Studies**: Detection and confirmation of dozens of planetary systems, including super-Earths, temperate rocky planets, and Saturn-mass objects, with an overall application to the statistical occurrence rates of exoplanets around low-mass stars. The planet occurrence rate is found to be $1.44 \pm 0.20$ planets per M dwarf for $1\, M_\oplus < M \sin i < 1000\, M_\oplus$ and $1 < P_\mathrm{orb} < 1000$ days [2302.10528].
- **High-Quality Spectral Library**: Creation of a public, telluric-corrected spectral library (TDTM), spanning $382$ M dwarfs and $\sim40,000$ spectra, with $R > 80,000$ and high S/N across $0.52$–$1.71$ μm, supporting RV extraction, photospheric modeling, chemical abundance determination, and atmospheric transmission/occultation studies [2310.14715].
- **Improved NIR RV Sensitivity**: Post-upgrade NIR channel enables robust detection of Earth-like planets exploiting the NIR flux peak of M dwarfs and diminishes the gap in sensitivity between red-optical and NIR, a key advance for studies of late-M dwarfs and activity-sensitive targets [2509.17966].

## 5. Collaboration, Consortium, and Data Distribution

The project is managed by a German–Spanish consortium comprising eleven core institutions, which ensure parity in both technical and scientific leadership [2503.05501]. 

- **Operational Model**: The consortium coordinates guaranteed and legacy time observations, while fostering a broader collaborative network with projects such as TESS, PLATO, MAROON-X, and ESPRESSO [2503.05501].
- **Data Release and Community Resource**: Legacy data releases (e.g., Data Release 1) provide calibrated spectra, processed RVs, and auxiliary data streams (stellar activity indicators, bisectors, etc.), catalyzing broader research in low-mass star science [2302.10528, 2310.14715].

## 6. Future Directions and Ancillary Science

CARMENES-PLUS is the platform for continuing upgrades and scientific exploitation:

- **Enhanced Calibration and Fiber System**: Further development of calibration etalons and fiber switches will permit simultaneous multi-source calibration and active monitoring of instrument drift, anticipated to push RV measurements to the sub-m/s regime in both VIS and NIR [2503.05501].
- **Ancillary Science Surveys**: The expanded infrastructure supports auxiliary programs (e.g., the KOBE survey for K dwarfs, CAVITY for galaxy studies), demonstrating the versatility of the instrument suite.
- **Synergy with Contemporary Facilities**: Strategic coordination with upcoming space missions and ground-based facilities will deepen the characterization of planetary atmospheres, test occurrence rate variations with metallicity and host properties, and enable detection of smaller, more temperate exoplanets.

## 7. Significance for Exoplanet Research

By achieving high thermal and instrumental stability in the NIR, improving calibration strategies, and expanding the survey’s temporal and spectral reach, CARMENES-PLUS enables:

- Detection of low-mass (Earth and sub-Earth) planets in the habitable zones of M dwarfs, reducing stellar noise contributions and identifying signals previously inaccessible due to instrument limitations.
- High-fidelity atmospheric studies through transit and occultation spectroscopy in both optical and NIR, offering constraints on molecular signatures and planetary dynamics.
- A comprehensive legacy of high-resolution, multi-epoch M-dwarf spectra, essential for both planetary science and detailed stellar astrophysics.

This suite of upgrades positions CARMENES-PLUS as a leading facility in the field of exoplanetary research, particularly for the characterization of planetary systems around low-mass stars, and as a model for future ultra-stable, high-resolution spectrographs in the optical and NIR domains [2509.17966, 2310.14715, 2503.05501].

Source: https://www.emergentmind.com/topics/carmenes-plus-project