logo All RW DDT exoplanets have been selected for observation
Rocky Worlds DDT : Status
Introduction
The Rocky Worlds DDT Program will use both JWST in the infrared and HST in the UV-to-optical to characterize rocky planets and their host M dwarfs.
On the JWST side, the program will gather time series observations aimed to detect planetary secondary eclipses (when the planet passes behind its host star from our perspective) at 15 µm using the MIRI instrument to measure thermal emission from its dayside.
On the HST side, the program will gather UV-to-optical spectra in order to characterize the high-energy output of the host M dwarf, using both the COS and STIS instruments in order to cover this broad spectral range. The versatile HST instrumentation will also allow us to view these data as time series, allowing the program to detect stellar flux variations that might arise, for example, from stellar flares.
Detailed Status Detailed Status

Program Information

HST (Cycles 32/33 allocation) JWST (Cycles 3/4 allocation)
goto HST 17904 Program Information goto JWST 9235 Program Information
download Download the HST 17904 APT file download Download the JWST 9235 APT file

SCHEDULING TIMELINE

Last update : 01AUG2025
2025
18 Aug
download Download the JWST Scheduling Report
2025
18 Aug
download Download the HST scheduling Report
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
DEC
2025
JWST CYCLE 3
CYCLE 4
HST CYCLE 32
CYCLE 33
2026
CYCLE 4
CYCLE 5
CYCLE 33
CYCLE 34
Eclipse 1
Observation #1
Exposure Duration: 5.38h
Planned for: July 08, 2025
Status: Archived
Eclipse 2 (Checkpoint 1)
Observation #2
Exposure Duration: 6.13h
Planned for: July 31, 2025
Status: Archived
Eclipse 3
Observation #3
Exposure Duration: 6.17h
Planned for: January 28, 2026
Status: On Hold
Eclipse 4
Observations #4 and #5
Exposure Duration: 7.3h
Planned for: January 30-31, 2026
Status: On Hold
Visits: 07 08
Orbits: 3
Instrument: STIS
Planned for: May 26 - Jun 03
Status: Not Observed
Visits: 07 08
Orbits: 3
Instrument: STIS
Planned for: Jul 15 - Jul 17
Status: Archived
Visits: 01 02 03 05
Orbits: 4
Instrument: COS
Planned for: Jan 26 - Feb 16
Status: Implementation
Visits: 01 02 03 05
Orbits: 4
Instrument: COS
Planned for: Mar 20 - Mar 30
Status: Implementation
Visits: 06
Orbits: 2
Instrument: STIS
Planned for: Apr 13 - Apr 24
Status: Implementation
Visits: 06
Orbits: 2
Instrument: STIS
Planned for: May 25 - Jun 08
Status: Implementation

QUICK LOOK

Observations Status
Last Update CIT Notes
download Eclipse 1 PASS
2025
05 Aug
Observations executed normally. Good data quality; detailed analyses ongoing.
download Visit 7 STIS/G140M FAIL
2025
08 Aug
Failed to lock guide stars. Orbit 1 was not exposed, no data. Orbits 2 and 3 exposed with HST blind pointing, but data quality is likely affected. HOPR approved (4 orbits).
download Visit 8 STIS/G140M PASS
2025
05 Aug
Lost lock on guide stars right after ACQ. Orbit 1 exposed but data is not usable. Orbits 2 and 3 were successful, with good data quality.
download Eclipse 2 PASS
2025
05 Aug
Observations executed normally. Good data quality; detailed analyses ongoing.

DATA ANALYSIS

download
download Visualize the available GJ-3929b data
Date Downloads
2025
29 Sep
download Eclipse 1 Data Analysis Report
2025
21 Oct
download Eclipse 2 Data Analysis Report
Date Downloads
2025
01 Oct
download HST Data Analysis Report

MAST

download
download Access the GJ-3929b data

program information
Scheduling Timeline
quick look
data analysis
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program information
Scheduling Timeline
quick look
data analysis
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program information
Scheduling Timeline
quick look
data analysis
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program information
Scheduling Timeline
quick look
data analysis
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program information
Scheduling Timeline
quick look
data analysis
mast
program information
Scheduling Timeline
quick look
data analysis
mast
program information
Scheduling Timeline
quick look
data analysis
mast
program information
Scheduling Timeline
quick look
data analysis
mast
Scheduling Strategy Scheduling Strategy
Two-Checkpoint Strategy

Because of uncertainties in orbital parameters, the timing of secondary eclipses can be off by minutes to hours. Instead of covering wide time windows for every eclipse—which is inefficient—we use a two-checkpoint strategy to optimize observations:

After a small number of eclipses (enough to detect an eclipse assuming a bare-rock planet, which produces one of the deepest possible signals), we evaluate the data under the first checkpoint.

  • CHECKPOINT 1:

    • If the eclipse is detected, we may shorten or reduce the number of remaining observations.
    • If the eclipse is not detected, we continue with longer observations to ensure detection.

After more eclipses, we arrive at a second checkpoint.

  • CHECKPOINT 2:

    • Here we assess whether the measured eclipse depth and uncertainty are sufficient to rule out the atmospheric models we aim to test (e.g., CO₂-bearing).

    • If yes, we stop observing. If not, we plan a final round of observations based on the accumulated data.

    This adaptive strategy ensures efficient use of telescope time while maintaining scientific rigor.

START INITIAL OBSERVATIONS CHECKPOINT 1 ECLIPSE DETECTION ? YES SHORTER OBSERVATIONS NO LONGER OBSERVATIONS CHECKPOINT 2 ATMOSPHERE RULED OUT ? YES NO FINAL OBSERVATIONS END

Conservative Noise Model

Initial eclipse count estimates were based on JWST ETC noise predictions, which are optimistic and do not fully account for real-world correlated noise.

We now apply a 1.25 × multiplier to ETC noise estimates, based on empirical results from Cycles 1-3. This ensures more realistic eclipse depth predictions and often increases the number of required eclipses.

Model Comparison: Bare Rock vs. CO₂ Atmosphere

Earlier strategies took a conservative view, comparing a high-temperature bare-rock planet with a generic atmosphere capable of redistributing heat.

With JWST/MIRI 15 μm photometry, we are most sensitive to CO₂-rich atmospheres, so we now directly compare the bare-rock case to the CO₂-rich case. This physically motivated model comparison often reduces the number of eclipses needed to distinguish between scenarios.

Pre-slewing Experiment

Fortune et al. (2025)arxiv reported tentative evidence that the amplitude of the time- series detector settling ramp (∼30-60 min) at 15 µm shows a somewhat repeatable and small amplitude when the filter wheel is in the MIRI LRS P750L position prior to swapping to the F1500W (15 µm) MIRI filter.

To test this hypothesis, the RW team is conducting a pre-slewing filter experiment with the RWDDT observations of GJ 3929 b. For this experiment, we have also included a MIRI external flat in the APT file before each eclipse observation. The objective of these external flats is to change to the P750L filter wheel position prior to slewing.

The setup of the pre-slew experiment is as follows:

1 finish previous visit,
2 setup instrument, wait for earliest start time,
3 slew to RW target, acquire guide star,
4 acquire target and perform science observations.

Other factors that may affect the settling slope are the stellar magnitude itself as explained in Connors et al. (2025)arxiv

We note that including the pre-slewing filter adds an additional 229 seconds to our observations.

PREVIOUS TARGET RW TARGET ACTION : MIRI FILTER : JWST finishes observing previous target RANDOM
PREVIOUS TARGET RW TARGET ACTION : MIRI FILTER : JWST changes MIRI filter P750L
PREVIOUS TARGET RW TARGET ACTION : MIRI FILTER : JWST slews to RW target P750L
PREVIOUS TARGET RW TARGET ACTION : MIRI FILTER : JWST waits until phase constraint is met F1500W (15 μm)
1 2 3 4
Date Changes
2025
04 Sep
Five new exoplanets selected for observation : TOI-198 b, TOI-406 c, TOI-771 b, HD 260655 c, and TOI-244 b
2025
18 Aug
A new Scheduling Strategy section was added and two Scheduling Reports are now available.
2025
17 Jun
Added targets GJ-3929 b, LTT-1445A b, LTT-1445A c, and LHS-1140 b
2025
10 Apr
Rocky Worlds DDT website goes live
2025
14 Mar
Webpage created
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2025 STScI Rocky Worlds Project