For Scientists: The Long-Term Plan

This is the current Long-Term Plan (LTP) for IXPE. IXPE is currently observing targets from GO Cycle 3. Category A targets are guaranteed to be observed, including the following A targets carried over from the previous cycle:

Prop Name RA Dec
2142 SS 433 287.9565 4.98272
The IXPE project expects to be able to observe ~50% of Category C targets. The Science Advisory Team requested that transient targets be added when and if they become bright. At such time, the LTP will be adjusted, attempting to minimize the impact on the overall plan; however, nothing is guaranteed.

IXPE is telemetry limited for bright sources and this requires that observations be handled slightly differently from the way most X-ray missions operate. If IXPE is observing a bright source that could potentially fill on-board storage, we shall divide the observation into multiple segments.

COLUMNS:
P: can be A, C, L, D or T. A and C targets were assigned by peer review. T is a ToO and D is DDT time. L denotes a large project. If an A target is bumped due to a ToO, it will be replaced. If a C target is bumped, it will likely be dropped from the plan.

S: This is a segment number. If segment is zero, then the observation has not been segmented.

Pnum: This is the GO proposal number. If the observation is a DDT or a calibration, then this number will be zero.

Name: This is a common name for the target.

RA: Target RA in decimal degrees.

Dec: Target Dec in decimal degrees.

Start: The Year-Month-Day The date the observation is planned to begin. The digits after the T is the start hour, in UT, truncated to a 6 hr interval.

buffer: This is an estimate as to how much data will stll be on the spacecraft when the observation ends in MB. The on-board storage can hold just over 4500 MB and when planning we keep the usage below 4000 MB.

P S Pnum Name RA Dec Start buffer
D 00000 GX 349+2 256.435 -36.4172026-03-02T00 2006.5
L 23215 1E 1547.0-54 237.725 -54.3072026-03-03T12 85.5
L 43224 MRK 501 253.468 39.7602026-03-10T12 0.0
A 33003 LS I +61 303 40.132 61.2292026-03-12T12 0.0
A 13261 4U 1916-053 289.698 -5.2382026-03-19T06 0.0
L 53224 MRK 501 253.468 39.7602026-03-24T12 0.0
A 23261 4U 1916-053 289.698 -5.2382026-03-26T18 0.0
A 13252 GS 1354-64 209.541 -64.7352026-03-28T18 2347.1
A 33261 4U 1916-053 289.698 -5.2382026-04-03T18 1438.5
A 13252 GS 1354-64 209.541 -64.7352026-04-07T06 2197.9
L 13224 MRK 501 253.468 39.7602026-04-09T06 1656.9
A 03250 MRK 421 166.114 38.2092026-04-11T06 0.0
A 43261 4U 1916-053 289.698 -5.2382026-04-22T00 0.0
L 23224 MRK 501 253.468 39.7602026-04-24T12 0.0
A 13079 SS 433 E2 288.543 4.9372026-04-26T12 0.0
L 33224 MRK 501 253.468 39.7602026-05-09T12 0.0
A 23079 SS 433 E2 288.543 4.9372026-05-11T12 0.0
L 13140 ARK 564 340.664 29.7252026-05-20T06 0.0
L 43224 MRK 501 253.468 39.7602026-05-22T12 0.0
L 23140 ARK 564 340.664 29.7252026-05-24T12 0.0
L 53224 MRK 501 253.468 39.7602026-06-04T06 0.0
NOTES:
Plan covers time up to 2026 June.
ToOs will cause planned times to shift around.
+ NASA Privacy, Security, Notices | Last Updated: March 19, 2026 | Author/Curator: Mitzi Adams, mitzi.adams @ nasa.gov