diff --git a/README.md b/README.md
index 0204ca9..845f4c4 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,8 @@
 - [aaaa/seeing-stars](aaaa/seeing-stars)
 - [aaaa/spacebook](aaaa/spacebook)
 - [comms/56k](comms/56k)
-- [ground-segment/phasors-to-stun](ground-segment/phasors-to-stun)
+- [comms/phasors-to-stun](comms/phasors-to-stun)
+- [payload/calendar](payload/calendar)
 - [payload/leakycrypto](payload/leakycrypto)
 - [satellite-bus/bytes-away](satellite-bus/bytes-away)
 - [satellite-bus/magic-bus](satellite-bus/magic-bus)
diff --git a/ground-segment/phasors-to-stun/README.md b/comms/phasors-to-stun/README.md
similarity index 96%
rename from ground-segment/phasors-to-stun/README.md
rename to comms/phasors-to-stun/README.md
index a375eb5..98533d5 100644
--- a/ground-segment/phasors-to-stun/README.md
+++ b/comms/phasors-to-stun/README.md
@@ -1,6 +1,6 @@
 # Phasors to Stun
 
-**Category:** Ground Segment
+**Category:** Communication Systems
 **Points (final):** 62
 **Solves:** 71
 
diff --git a/ground-segment/phasors-to-stun/signal.png b/comms/phasors-to-stun/signal.png
similarity index 100%
rename from ground-segment/phasors-to-stun/signal.png
rename to comms/phasors-to-stun/signal.png
diff --git a/ground-segment/phasors-to-stun/urh1.png b/comms/phasors-to-stun/urh1.png
similarity index 100%
rename from ground-segment/phasors-to-stun/urh1.png
rename to comms/phasors-to-stun/urh1.png
diff --git a/ground-segment/phasors-to-stun/urh2.png b/comms/phasors-to-stun/urh2.png
similarity index 100%
rename from ground-segment/phasors-to-stun/urh2.png
rename to comms/phasors-to-stun/urh2.png
diff --git a/ground-segment/.gitkeep b/ground-segment/.gitkeep
new file mode 100644
index 0000000..e69de29
diff --git a/payload/calendar/Dockerfile b/payload/calendar/Dockerfile
new file mode 100644
index 0000000..65730c7
--- /dev/null
+++ b/payload/calendar/Dockerfile
@@ -0,0 +1,32 @@
+FROM ubuntu:18.04
+
+RUN apt-get update -y && apt-get install -y \
+  cmake \
+  freeglut3 \
+  freeglut3-dev \
+  gcc \
+  g++ \
+  git \
+  iproute2 \
+  libffi-dev \
+  libgdbm-dev \
+  libgdbm5 \
+  libgstreamer-plugins-base1.0-dev \
+  libgstreamer1.0-dev \
+  libncurses5-dev \
+  libreadline6-dev \
+  libsmokeqt4-dev \
+  libssl-dev \
+  libyaml-dev \
+  net-tools \
+  qt4-default \
+  qt4-dev-tools \
+  ruby2.5 \
+  ruby2.5-dev \
+  vim \
+  zlib1g-dev
+
+RUN apt-get install -y bundler
+
+WORKDIR /cosmos
+CMD /bin/bash
diff --git a/payload/calendar/README.md b/payload/calendar/README.md
new file mode 100644
index 0000000..83329e6
--- /dev/null
+++ b/payload/calendar/README.md
@@ -0,0 +1,78 @@
+# That's not on my calendar
+
+**Category:** Payload Modules
+**Points (final):** 80
+**Solves:** 52
+
+>Time for a really gentle introduction to cFS and Cosmos, hopefully you can schedule time to learn
+>it!
+>
+>Build instructions:
+>
+>$ ./setup.sh $ source ~/.bashrc $ rm Gemfile.lock $ bundle install
+>
+>Hint: You will need to enable telemetry locally on the satellite, the udp forwarder will provide it
+>to you as TCP from there
+
+## Write-up
+
+by [haskal](https://awoo.systems)
+
+Two files are provided, one is a [COSMOS](https://cosmosrb.com/) directory tree for accessing a
+virtual satellite running [NASA's Core Flight System](https://cfs.gsfc.nasa.gov/) that can be booted
+up using the provided netcat endpoint. COSMOS is an open-source command and control framework for
+satellites using cFS. Booting up COSMOS is enormously complicated, so Docker can be used to automate
+the setup. We adapted the Ball Aerospace COSMOS Docker image, and created a script to configure
+COSMOS to connect to the CTF's satellite instance automatically by writing the configuration file at
+`cosmos/config/tools/cmd_tlm_server/cmd_tlm_server.txt`.  When COSMOS is successfully connected to
+the CTF instance it looks like this (no themes were installed in the Docker container so it looks
+like Windows 95, I'm so sorry,)
+
+![Main COSMOS screen](cosmos1.png)
+
+The second file is an archive of some JSON configuration for the satellite operating system.
+Importantly, it contains the types of telemetry messages the satellite can send, and the default
+scheduler table that configures when the satellite sends the messages. There is a telemetry packet
+that sends us the flag configured here
+
+```json
+      {"message": {
+         "name":  "KIT_TO_SEND_FLAG_MID",
+         "descr": "Super Secret Flag Sending Telemetry Message",
+         "id": 42,
+         "stream-id": 33304,
+         "seq-seg": 192,
+         "length": 256
+      }},
+```
+
+As hinted in the description, we can send a KIT_TO ENABLE_TELEMETRY command using the COSMOS command
+sender. KIT_TO is the subsystem for Telemetry Output, and it has commands available to control the
+telemetry sending.
+
+![COSMOS sending an ENABLE_TELEMETRY command](cosmos2.png)
+
+However we find that even after telemetry is enabled, we're not getting the flag telemetry even
+though we start to receive other types of telemetry messages.
+
+![COSMOS telemetry viewer, we have 0 flag packets](cosmos3.png)
+
+This is because, if we look back at the JSON config we find that the scheduler doesn't have any
+slots where it sends flag telemetry packets. The key part of this challenge is that the scheduler
+can be configured at runtime using commands for KIT_SCH (the scheduler subsystem), as we found out
+by exploring the available commands in COSMOS. Particularly there is a command LOAD_SCH_ENTRY that
+allows us to overwrite one of the scheduler entries. We can use the command sender to send this
+command and load slot 0, activity 0 (or any slot, it doesn't matter) to be for message ID 42 (the
+flag packet ID), and to be enabled (1).
+
+![COSMOS sending this LOAD_SCH_ENTRY command](cosmos4.png)
+
+Once we write the scheduler entry, the satellite will start sending COSMOS flags, which can be seen
+in the Packet Viewer.
+
+![COSMOS packet viewer showing the flag](cosmos5.png)
+
+## Resources and other writeups
+
+ * <https://cosmosrb.com/>
+ * <https://cfs.gsfc.nasa.gov/>
diff --git a/payload/calendar/cosmos1.png b/payload/calendar/cosmos1.png
new file mode 100644
index 0000000..ccfbc64
Binary files /dev/null and b/payload/calendar/cosmos1.png differ
diff --git a/payload/calendar/cosmos2.png b/payload/calendar/cosmos2.png
new file mode 100644
index 0000000..a3c2f3a
Binary files /dev/null and b/payload/calendar/cosmos2.png differ
diff --git a/payload/calendar/cosmos3.png b/payload/calendar/cosmos3.png
new file mode 100644
index 0000000..9261320
Binary files /dev/null and b/payload/calendar/cosmos3.png differ
diff --git a/payload/calendar/cosmos4.png b/payload/calendar/cosmos4.png
new file mode 100644
index 0000000..1437ec9
Binary files /dev/null and b/payload/calendar/cosmos4.png differ
diff --git a/payload/calendar/cosmos5.png b/payload/calendar/cosmos5.png
new file mode 100644
index 0000000..dfc4370
Binary files /dev/null and b/payload/calendar/cosmos5.png differ
diff --git a/payload/calendar/launch-docker.sh b/payload/calendar/launch-docker.sh
new file mode 100644
index 0000000..a366155
--- /dev/null
+++ b/payload/calendar/launch-docker.sh
@@ -0,0 +1,3 @@
+#!/bin/bash
+
+docker run -it -e DISPLAY -e QT_X11_NO_MITSHM=1 --net=host -v $PWD/cosmos:/cosmos cosmos2 bash