Interplanetary Control Echo Message

1. Abstract

ICEM defines an experimental procedure for verifying the physical availability of remote astronomical nodes where conventional ICMP transport is unavailable.

The first observed implementation used the ICEM/EM Earth–Moon profile. The implementation was identified after delivery and is documented here as observed behavior, not as an approved transmission method.

2. Request

The first observed ICEM/EM request consisted of one spent launch-vehicle stage on an Earth–Moon trajectory. For protocol purposes, the stage is treated as a single macroscopic packet.

TYPE:        ECHO REQUEST
SOURCE:      EARTH
DESTINATION: MOON
PROFILE:     ICEM/EM
PACKETS:     1
PACKET SIZE: ~3.9 t

3. Delivery

Delivery was confirmed on 5 August 2026. Orbital observations acquired by Danuri before and after the event showed a local surface change at the predicted destination.

No crater dimension is specified by this document. Reachability requires evidence of delivery; geometric consensus is outside the current profile.

DELIVERY:             CONFIRMED
REMOTE HOST:          REACHABLE
SURFACE MODIFICATION: OBSERVED
ECHO RESPONSE:        NOT RECEIVED

4. Response and Timeout

No echo response was recorded during the initial response window.

Following that interval, the remote node is expected to affect visibility of the upstream resource SUN during the total solar eclipse of 12 August 2026.

HCRD has not established a causal relationship between the request and the subsequent event. Temporal adjacency is retained as a diagnostic observation only.

INITIAL RESPONSE WINDOW: 7 days

5. Security Considerations

ICEM implementations using macroscopic physical payloads may modify the receiving node upon delivery.

Production use without prior coordination with the remote node is therefore discouraged. The absence of a rejection response MUST NOT be interpreted as consent.

6. Compatibility

ICEM is not wire-compatible with ICMP. Support for the Earth–Moon profile has been observed in one direction only.

ICMP COMPATIBILITY: NO
ICEM/EM SUPPORT:    OBSERVED
REMOTE ACK SUPPORT: UNKNOWN

7. Status

The experiment is considered successful for reachability verification.

Bidirectional protocol compatibility remains unconfirmed. ICEM/EM retains Experimental status and is not recommended as a general-purpose transport.